Resolving "Navigation to the webpage was canceled" with Compiled HTML Help files (.chm)

I'm working with a SDK from a vendor that we have partnered with.  They provide the SDK as a download that I grabbed over FTP with Internet Explorer.  The SDK has a .NET assembly to use, some sample code, and documentation in a .chm help file.  It's all neatly bundled in a .zip files, nothing too esoteric.

Since Windows directly supports .zip files, I used Windows Explorer (Windows 7) to copy the files from the .zip file to new folder.  I then launched the help to examine some new functions the vendor had added for me.  The help file loaded up, but I couldn’t access anything.  It looked like this:



At first I thought the file was corrupt, but then I realized what was going on.  With Windows Explorer, I selected the .chm file and right-clicked on it and selected “Properties”.



If you look at the section that is highlighted in green, you’ll see the text ”This file came from another computer and might be blocked to help protect this computer.”.  With Windows XP SP2 and later operating systems, the file’s zone information is being stored with the file as stream.  A stream is a separate resource stored with the file, just not exactly in the file.  Separate resource streams is a feature of the NTFS file system.  Since the .zip file had been downloaded with Internet Explorer, the .chm file was treated as if it had been downloaded directly. 

This is actually a good thing.  By default Internet Explorer will not let you run content from your local disk without your expressed acceptance.  Since the Internet Explorer rendering engine is used to render the pages of the .chm file, it’s going to block pages that came from the Internet Zone.

You have a couple of ways of fixing this.  One way would to disable the blocking of local content.  I don’t think that’s a safe way to operate so I’m not going to describe how to do that.  In the file Properties dialog, there is an “Unblock” button.  Click that button and you can remove the Zone block.

Another way would be to use a command line tool and remove the Zone Identifier resource stream.  SInce NTFS file streams pretty much invisible to the casual eye, you can grab a free tool to trip that data out for you.  Mark Russinovich’s Sysinternals collection of utilities includes a nice little gen called streams.  It’s a handy little utility.  It will list what streams are associated with a file or folder and you delete them.  Recursively and with wild cards too.  One of the thinks I like about Systinternal command line tools is that you can run them without a parameter to get a brief description of what it does and how to use it:

Streams v1.56 - Enumerate alternate NTFS data streams
Copyright (C) 1999-2007 Mark Russinovich
Sysinternals - www.sysinternals.com

usage: \utils\SysInternals\streams.exe [-s] [-d] 
-s     Recurse subdirectories
-d     Delete streams

When I ran streams on my .chm file, I saw the following:

streams.exe SomeSdk.chm

Streams v1.56 - Enumerate alternate NTFS data streams
Copyright (C) 1999-2007 Mark Russinovich
Sysinternals - www.sysinternals.com

C:\dev\SomeSdk.chm:
:Zone.Identifier:$DATA       26

You can also get a listing of the resource streams if you use the “/R” parameter with the DIR command. To see the contents of the stream, you can open it with notepad with syntax like this:

notepad MySdk.chm:Zone.Identifier

That would display something like this:

[ZoneTransfer]
ZoneId=3

Any value of 3 or higher would be considered a remote file.  So I ran it one more time, just with the –d parameter and got this:

streams.exe -d SomeSdk.chm

Streams v1.56 - Enumerate alternate NTFS data streams
Copyright (C) 1999-2007 Mark Russinovich
Sysinternals - www.sysinternals.com

C:\dev\SomeSdk.chm:
Deleted :Zone.Identifier:$DATA

Once I did that, my help file was unblocked and ready to be used.

Why www.nbc.com wont load with IE7 on Vista (and how to get around it)

My kids wanted to watch the Olympic swimming events going on in Beijing.  Since NBC is streaming all the venues, I figures I would just fire up the web browser and wander over to www.nbc.com.   We have a “family” pc that everyone can use and it runs Vista Home Premimum (32-bit), with Service Pack 1 installed.  Since I knew that NBC was going to be using the Microsoft stack with Silverlight to stream the video, I figured I would have the least amount of headaches with Internet Explorer 7.  Wrong!

When I entered in http://www.nbc.com into IE, I got the following error: “Internet Explorer cannot display the webpage”.  I figured I mistyped the URL, that wasn’t it.  Out of the relatively small combinations that the letters N, B, and C can be arranged, I did have the right URL.  Could it be that NBC.com was done?  Nope, I tried “ping –n 1 www.nbc.com” and received the following

Pinging a1669.g.akamai.net [128.242.186.219] with 32 bytes of data:                               
                                                                                                  
Reply from 128.242.186.219: bytes=32 time=44ms TTL=55                                             
                                                                                                  
Ping statistics for 128.242.186.219:                                                              
    Packets: Sent = 1, Received = 1, Lost = 0 (0% loss),                                          
Approximate round trip times in milli-seconds:                                                    
    Minimum = 44ms, Maximum = 44ms, Average = 44ms                                                 

That tells us that their site is live and responding to requests.  Just for giggles, I launched FireFox 3 and entered in the URL.  Sure enough, that worked just fine.  What was the problem with nbc.com and IE7?  I did a search with Google (and Yahoo for a change of pace) and saw that a number of people were reporting the same problem.  No one knew the cause and the only resolution was “just use Firefox”.  Normally, that would be an acceptable answer for me.  Today, I’m feeling a bit cranky and I want to know what the problem is between nbc.com and IE7.  The odds are it’s something trivial on the nbc,com side.  We haven’t had any problems with IE7 on Vista before.

I did notice that a lot of people reporting the problem had Tablet PC’s. I don’t have a Tablet PC, it’s just an plain ol’ Dell desktop.  But I did install a Wacom Bamboo tablet and installing it’s drivers did activate some user input functionality in Vista that wasn’t there before.  Why would this affect the browser?  As it turns out, when Vista thinks it’s now a Tablet PC the user agent string sent by IE changes.

Here’s the typical user-agent string sent by IE7 for various operating systems.

For Windows XP SP2: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1)

For Windows 2003 Server: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.2)

For Windows Vista: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0)

Note, these are the base strings, different applications can change or add to these values.  On my machine, the user agent has some information:

Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0; SLCC1; .NET CLR 2.0.50727; Media Center PC 5.0; .NET CLR 3.0.04506; .NET CLR 3.5.21022; Tablet PC 2.0; Creative ZENcast v2.01.01)

That says that I’m running IE7 on Vista, with .NET 2, 3, and 3.5 installed.  Media Center extension are installed, it thinks it’s a Tablet PC, and I have Creative’s Zencast (a podcast download app).

Notice the text in bold, “Table PC 2.0”.  When that text is submitted to www.nbc.com as part of the user agent, the website is doing some sort of re-direct that is failing.  So we have what appears to the cause of the problem, now how do we fix it.  I tried faking out the user agent string with a download from Microsoft called the User Agent String Utility, version 2.  Don’t event bother with that one.  It opens up a new browser window that has been tweaked to report itself as IE 6.0 but that’s the only part of the user agent string that gets modified.  It still uses “Table PC 2.0”, so the problem still remains.

In theory, you can edit the list of items that get tacked on the user agent string by hacking at the registry.  With IE7, the list of fields added to the user agent string are defined as REG_SZ values in HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\5.0\User Agent\Post Platform.  I tried removing “Tablet PC 2.0” from the list, but the OS kept putting it back in.  Plus, we really shouldn’t have to modify our systems, the problem is due to www.nbc.com not sniffing the user agent string correctly.

I did a little searching on the Internet and I found a working solution here.  Instead of using www.nbc.com as the starting URL, use www.nbci.com.  That site bypasses the user agent check and it allowed me to the live feeds of the Olympic events.  A very simple solution, but a typical home user would never figure it out on his own and just blame Vista for it.

IPv6 and Vista

The other day, I read a post that Carl Franklin had made on his blog about a new Vista laptop that he had to buy on short notice.  The gist of his post that Vista ran pretty well, but he did tweak some of the settings.

One of the settings that Carl had tweaked was to disable IPv6 on all of the network adapters.  For some reason that jumped out at me.  I posted a comment on his blog asking why he did it.  I'm all for disabling services that are not being used, but I like to know what the reason is behind it. 

I did a quick scan through Google, and initially found many hits for how to disable IPv6 with very little explanation on why you should do it.  Carl responded to my comment that he had heard anecdotal evidence that IPv6 can cause conflicts under Vista.

For me, the decision to disable IPv6 on my Vista boxes boils down to two questions:  Do I need IPv6 functionality?  If I don't need IPv6, does having IPv6 enabled cause any problems under Vista?  Time to go back to Google and due some more searching.

One bit of trivia:  While I was searching for why you would want to disable IPv6 on Vista, I came across a few articles about how Google owns a large block of IPv6 space that works out to be 7.9 x 10²⁸ IP addresses. That's a large number, no matter how you slice it.   Why does our Google Overlord need that many addresses?

I've seen the badge below displayed on a few sites. 

Pretty scary looking, huh?  There is a real concern with the number of IPv4 addresses being used up.  At the current rate of assignment, we just have a few years left before the all of the addresses have been assigned.  That's why they came up with IPv6, to provide for a virtually unlimited number of IP addresses.  Even with Google hogging billion and billions of IPv6 addresses, we'll still more than enough to serve this planets needs for the for seeable future.  Right now, the continued use of NAT allows more users to share the same IP address. 

We are seeing all of the IPv4 addresses being assigned, but that doesn't mean that they are all being used.  If you look at the global IPv4 allocation list, you'll see that large chunks of the IPv4 space is in the hands of a small number of companies.  For example, Apple owns all the 017.xxx.xxx.xxx addresses.  That's over 16 million distinct, global IP addresses.  What are they doing with all those addresses?  And some people still question the need for IPv6 in the first place. 

But I digress, I think we'll be safe with just IPv4 addresses for the next few years.  At this point, there are no IPv6 only addresses that I want to visit.  They exist, I just don't need to visit them.  So the answer to my first question is: No, I don't need IPv6.

So what about leaving IPv6 enabled in Vista?  What does that cost me?  I read about some reports early in the Vista release with IPv6 issues.  Some of that could be attributed to "version 1.0" network drivers.  I did read some reports of http://localhost not working with IPv6 enabled. 

On an IPv6 enabled box, localhost will evaluate to ::1, not the 127.0.0.1 that we call home.  That is what defined for localhost in %SystemRoot%\system32\drivers\etc\hosts as the IPv6 adddress for localhost.  This apparently causes a problem when testing locally hosted websites.  If you remove (or better yet, just comment out the ::1 entry from the hosts file, that was reported to allow web development to continue using localhost and IPv6 installed.

Klaus Graefensteiner has a pretty good explanation of why this is happening.  As noted elsewhere, he recommends editing the hosts file as the work around. I haven't done any web development on my Vista box, I can't verify that this is still an issue.  I'm actually planning on doing some web development work from my home machine in the near future, issues with localhost will pop up pretty much immediately. 

As far as I can tell, the answer to my second question is "maybe".  If the only issue is the localhost issue, then I'll address it through editing the hosts file as opposed to disabling IPv6 altogether.

I did see the value of one point that Carl made.  If the service is not being used, then disable it.  It's not enough of an issue for me, but resources are limited, then you want to pick off the low hanging fruits from the list of running services.  If you do actually want to disable IPv6 in Vista, it's pretty easy to disable or enable IPv6 support (from numerous sources, this one from TechSupportForum.Com)

1. Go to Start and type in "ncpa.cpl" (without the quotes) and press Enter
2. Right click on each network connection and select "Properties"
3. Remove the checkmark from the box next to "Internet Protocol Version 6 (TCP/IPv6)
4. Click OK to exit the dialog

Lather, rinse, and repeat for each network connection. IPv6 will still remains active for routing and tunneling.

To complete disable IPv^ in the system, you'll need to add a registry.  Go to registry and create DWORD parameter "DisabledComponents" in HKLM\SYSTEM\CurrentControlSet\Services\Tcpip6\Parameters and set it to a value of 0xff and restart the system.

Just remember one thing, if you disable IPv6, you will not be able to use Windows Meeting Space or any application that relies on the Windows Peer-to-Peer Networking platform or the Teredo transition technology.

Bonus Firefox tip:  You can disable Firefox's usage of IPv6 with out disabling IPv6 for the rest of the system.

In Firefox, type about:config and then in the filter box type dns. You'll see an entry named "network.dns.disableIPv6".  Double-click that line so that it reads True, which will effectively disabled IPv6 for Firefox.  You'll need to restart Firefox for this change to take effect.

Uninstall IE8 Beta before installing XP SP3

If you running the beta version of Internet Explorer 8 (IE8) under Windows XP, the word is to uninstall IE8 before installing Windows XP Service Pack 3 (SP3).  Once SP3 has been installed, you will be unable to remove IE8 (and IE7).  The reason for this is documented on the IEBlog with this post.  Basically, when you install IE7 or IE8, the existing IE6 (version of IE that comes with XP) is backed up to an uninstall folder.  SP3 includes an updated set pf IE6 files.  If you were to uninstall IE7 or IE8 after installing SP3, you would have a mixture of IE6 files from pre-SP3 and the bits installed as part of SP3.  That would cause all sorts of problems and Microsoft disables the uninstall option for IE7 and IE8 after SP3 is installed.

Not being able to remove IE7 isn't a big issue.  If you have IE7 in place, the odds are that you are used to it and will not be removing it.  The beta version of IE8 is another situation altogether.  When the next beta or release candidate or even the actual release comes out, you'll want to uninstall the beta version first.  It's just the prudent thing to do.  Well not exactly, it's much safer to install anything labeled beta in a virtual machine.  But if you have the IE8 beta installed on a XP box and you are planning on installing SP3, you'll want to remove the beta before installing SP3.  In fact, Microsoft will not offer SP3 through Windows Update if it detects the IE8 beta on your machine.  Once SP3 has been installed, you can install the IE8 beta again.