For a better understanding of this issue, I would like to have the following information.
1.Did you download the .CHM file from the Internet?
2.Did you get any error message while opening the .CHM files?
3.For which program are you trying to view the CHM files?
The CHM files usually refuses to load appropriately when they are flagged as downloaded from an un-trusted source such as Internet. So, let’s check if the issue is due to this by unblocking the file. You may try the following steps
to unblock the .CHM files and check if that resolves the issue.
Unblock the CHM files and check
a)Right-click the .CHM file that you are trying to view and choose “Properties”.
b)On the “General” tab, click the button labeled "Unblock"
c)Click on “Ok”
If the issue still persists, please do get back to us with the result of the above steps and with all the additional information regarding this issue. We’ll be glad to assist you further.
Regards, Rajesh Govind - Microsoft Support Engineer