Problem: chm file can be opened locally but not from network drive. Might be an IE7 or windows security patch problem?

Solution:
Change registry:

REGEDIT4
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\HTMLHelp]
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\HTMLHelp\1.x\ItssRestrictions]
"MaxAllowedZone"=dword:00000003

from MS support solution 2

I used to have a “MaxAllowdZone = 2″, which means opening chm file from internet is not allowed. After changing it to 3, problem went away.

For some reason, this value comes back to default value 2 everyday on my workstation. Might because our company’s policy, so I created a batch file to re-set it on my startup.

reg add HKLM\SOFTWARE\Microsoft\HTMLHelp\1.x\ItssRestrictions /v MaxAllowedZone /t REG_DWORD /d 3 /f