How to open .chm file in Windows 7

Are you trying to figure out how to open a .chm file in Windows 7? Learn the tips to work with .chm files in Windows operating system.

Do you see 'Page not displayed' or 'Navigation to the web page was cancelled' when you try to open a .chm file?

I have found that you do not need any software to view the file. These files coming from third party server are by default blocked. Hence you just need to unblock them in many instances to view them.

1. Right click the file and select 'Properties'
2. Click Unblock

Other known issues for error with .chm file

1. Check for any hash/sharp symbol in the filename. Rename your file without using any symbols. This is a known bug with all Window versions.
2. CHM viewer component not registered on your PC - Run regsvr32 hhctrl.ocx in the command line(Start>>Run) to register the library in the system.

When the .chm file is on other network drive:

1. Go to Run and type regedit
2. Locate HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\HTMLHelp\1.x\ItssRestrictions. Create the registry key, if it does not exist
3. Right-click ItssRestrictions, select New, and then click DWORD.
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.
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.

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Guest Author: NeoMod08 Jan 2012

Dear Author,

thankyou very much for this precious info!!! Those few lineas at the beginning of this article just saved my day!

( platform: win7 x64 enterprise )

Best Regards!!!

Guest Author: jiju25 Jan 2012

Thanks... It helped me to open .chm file... thanks

Guest Author: gaurav28 Mar 2012

thank u that was so much helpful..

Guest Author: Sam Bard29 Oct 2012

Thanks a lot.You rock :)

Guest Author: Dan11 Nov 2012

I could not find any option to unblock a chm file on my local windows 7 64bit home system, and I followed your regedit commands exactly without any change. I still get the error message when I double click a .chm file (navigation to webpage was cancelled). But if I download/save the chm to my local machine, I am able to open it. Is a reboot or logout/login required after editing the registry?

Guest Author: Charles27 Mar 2013


I appreciate the response above, I have tried the above option but it does not seem to help me view my .chm files on a shared network drive, I am using windows 7 Ultimate 64-bit

Guest Author: Anusha11 May 2013

Thank you so much. I am really thinking to download files which can read the chm file but the unblock idea worked very well.

Thanks once again

Guest Author: Abdi19 Jan 2014

Thank you so much. This opened two important books for me that I could not open. Thanks a lot God bless you.

Guest Author: John26 Jan 2014

Many thanks, unblock worked fine. Windows 7 no help at all in not asking if I wanted to unblock.

Guest Author: John Smith03 Feb 2014

Another solution ( from )

Run the following lines:

regsvr32 %systemroot%\system32\hhctrl.ocx
regsvr32 %systemroot%\system32\itss.dll

Guest Author: rishabh20 Feb 2014

Thanks a lot for offering this perfect solution.

Guest Author: Ka16 Jul 2014

Great, thank you

Guest Author: meandme04 Feb 2015

Thanks! That works.

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