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 -

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 -

: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:


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 -

Deleted :Zone.Identifier:$DATA

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

A Disaster Recovery Plan is useless if you don’t verify that it works.

I was just reading a Computerworld article about how American Eagles Outfitters just went through an eight day web outage (originally covered by StorefrontBacktalk).  It started when some hardware failed, then the backup hardware failed, then the software designed to restore the data to the replacement hardware failed, and finally their disaster recovery site wasn’t ready.  They were doing the right things: backups, backups of backups, and an alternate site in case their main site is dead in the water.  It just didn’t work when it was needed.  They were flat out down for 4 days, and then only had minimal functionality for another four days.

Being down or not fully functional for 8 days is a huge amount of time if you are an online retailer, but it would be catastrophic for just about any company to their network down or seriously hobbled for over a week.  How effective would your company be today if you had were isolated computers, without any Internet access.  On the plus side, that means no Farmville, which would actually be a productivity gain.  But life without email, that’s another story.  For most companies, email is a basic tool of business and you can’t get by without it.

You need to have a disaster recovery (DR) plan.  You have to plan on the basis that a meteor has taken out your building one night, and all your business tools are gone.  You need to backup the key assets of your network.  If it’s on a computer and you need it, then it should be backed up.

Those backups need to be off site.  If your office complex is under 8 feet of water, those backup tapes are going to under 8 feet of water too.  Your IT staff needs to be taking those backups offsite.  It could as simple as taking the backups to a safe deposit box, or a live backup of your system to alternate location.

You also need a disaster recovery site.  You need backup network equipment that you can bring online with your current data.  It could be a dedicated hosting facility or a rack of servers at another location if your company has more than one office.  The important thing is that it’s periodically tested.  A DR site is no good if it doesn’t work.  That is what was the biggest failure for American Eagles Outfitters, their final point of protection wasn’t ready and had never been tested.

You also need to plan for the human resources.  If a disaster strikes your office, you need to have a plan to contact all of the employees and arrange for alternate office facilities.  if your DR site is up and running, it wont do you any good if none of your employees can access it.

Being prepared with a DR plan is not a one time task or expense.  IT departments need to have the support and resources to keep the plan updated.  And they need to be able to test it on a period basis.  A plan that works today with X amount of data, could be utterly useless next year when you have Y amount of data.  You need to be able validate that your backups worked and that they can be restored in a reasonable amount of time.

That’s the hard sell, with companies looking to keep their costs down, it’s hard to keep items like this in the IT budget.  I look at what happened to American Eagles Outfitters as a cautionary tale of what happens if you skimp on an IT budget. 

The money quote for why the DR site was not fully functional:

“I know they were supposed to have completed it with Oracle Data Guard, but apparently it must have fallen off the priority list in the past few months and it was not there when needed.”

Penny wise, pound foolish.