This blog post provides simple step-by-step solutions to getting Windows Help files to display under Windows Vista/ Windows 7.
NOTE: Microsoft Help Viewer is not installed as standard in any of the newer operating systems (Microsoft is actively discouraging it's use). In order to add this feature to you system consult this Mircosoft Knowledgebase Article;
This gives you the information you need to install the Help viewer on Vista/7/2008/etc. Without it you will not be able to view help files *at all*.
The message which this knol is attempting to solve when viewing a Help file is;
The error message reads;
"Cannot display this help file. Try opening the help file again, and if you still get this message, copy the help file to a different drive, and try again".
First of all it's just "information" (not an error) and whilst copying it to a drive with different permissions could solve the problem the fact that you're seeing this error in the first place indicates that it might not.
The problem is caused by the file not being from a "known" source and being in a location (on your hard drive/ network share/ USB stick/ etc) where items with a unknown source cannot be run. Windows in effect treats Help Files in the same was as it does with executables. The message is quite correct in that moving it to a location where this restriction isn't enforced will solve the problem, it's just pretty unlikely there is one!
Anyway to solve the problem right-click the file and select "Properties" (usually at the bottom).
I've highlighted the "Security" section. Click "Unblock". Click "OK".
You should now be able to open the file.