Friday, July 06, 2007

Open CHM Files from Network drive

I experienced a problem recently when trying to open a .CHM help file from a network drive.

The file opened, and I could navigate the topic tree, but I just got a "Page could not be displayed" IE page in the right pane.

I found the solution to my problem at, in comments left by Anish and Jordan Wiseman

I have repeated this info here:

1. Click Start, click Run, type regedit, and then click OK.
2. Locate and then click the following subkey:
Note If this registry subkey does not exist, create it by using Steps 2a and 2b in Method 1.
3. Right-click the ItssRestrictions subkey, point to New, and then click DWORD Value.
4. Type MaxAllowedZone, and then press ENTER.
5. Right-click the MaxAllowedZone value, and then click Modify.
6. In the Value data box, type a number from 0 and 4, and then click OK.
7. Quit Registry Editor.

Value Setting
0 My Computer
1 Local Intranet Zone
2 Trusted sites Zone
3 Internet Zone
4 Restricted Sites Zone

For most CHM files, the value of 1 should be enough to allow use without opening up access from/to remote CHM files in email/internet locations.

Easy, peasy!


  • I've seen this solution in numerous places, but it does not work for me. I can open the CHM on my hard drive and view it just fine, but when I copy it to a network share, I cannot open it.

    By Blogger Karla, at 4:01 pm, January 22, 2008  

  • This is something that I haven't had an issue with since creating this post, but your comment prompted me to try it on my new install of Vista.

    It seems that the same problem exists, but using the steps in the post enabled me to view it correctly.

    I can't think of anything else to suggest other than posting the resultant .reg file from the changes that I made:

    Windows Registry Editor Version 5.00


    Also, I guess that it could possibly be some sort of permissions issue?

    By Blogger Carl, at 4:22 pm, January 22, 2008  

  • See:

    To quote, "You still cannot access .chm files by using a URL. Although we do not recommend that you do this, you can access the files by following example 2 and setting the "MaxAllowedZone" to three or larger. This is because the .chm file uses the Internet Explorer cache and every page that comes from the cache uses the Internet zone. Therefore, we highly recommend that you use the UNC path to access the Help files as previously described."

    By Blogger HighDesert, at 3:28 pm, June 11, 2008  

  • Hi,

    Just wanted to say that I've been searching the net for a solution on how to view chm-files from a network share on my Vista-system. None of the registry editing i found worked for me and I don't want to copy them to my local drive. If you have the same problem as me there is one simple solution: use a different chm-viewer. I'm using xchm ( and it is working perfect.

    By Blogger Björn, at 10:09 pm, March 29, 2009  

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