When I click on "Help" nothing happens. I am using Pegasus Mail 4.73 on Windows 7 Pro.

This is the content of a recent discussion on the PM-WIN listserv that may be helpful.

Regarding the help file issue, I don't know what the problem is but
you can try opening it manually to see if that works. This would rule
out something in Win10 preventing the help file executable (SHOWHELP.EXE)
from running. To do this you can either drag and drop the WINPM-32.PHC
file onto SHOWHELP.EXE or run the following command:
C:\PMAIL\PROGRAMS\SHOWHELP.EXE WINPM-32.PHC

Thanks. I did the latter and it worked. After a bit more playing
about it appears the default help window size/state had got into a
weird mode that prevented it being fully visible, I have now fixed
this by maximising then re-sizing it.

Brian Fluet, thank you for the response. The move of winpm-32.phc does work. It would be nice if the button would do the same.

Opening winpm-32.phc with showhelp.exe is a test that confirms the functionality of the help system is working. I don't know what might be preventing it from being invoked from within Pegasus Mail.
What "button" are you referring to?
What happens when you go to the Help pull-down menu and select Help index?

When I select Help and Specific Help an additional Pegasus icon appears on the Windows task bar. This icon is blank-it contains no information. I can close it by clicking its' red X. This is the result of clicking any of the options under Help except for: Visiting the Pegasus Mail Website, Visit the Pegasus Mail Community, and About Pegasus Mail.

Sounds like the Help window is out of screen: At first figure out your new mailbox path via menu Help => About Pegasus Mail => Info => New mailbox location. Now shut down Pegasus Mail, go to this new mailbox directory and open a file called STATE.PMJ with a simple plain text editor (no office application!), search for an entry starting with PMHELP5= in the [General] section and delete the whole line (only this one!), then save this file and restart Pegasus Mail: Next time you attempt to open help it should become visible again.

Michael, that works-all the Help selections are now active. Thanks very much.

You're welcome!

When I try to save I get this message:

"You do not have permission to open this file. See the owner of the file or an administrator to obtain permission."

If you are talking about saving an edited STATE.PMJ file you can check permissions to make sure you have modify rights but this gets routinely modified by Pegasus Mail so permissions shouldn't be the problem. Make sure that its isn't being used by another program (Pegasus Mail should be closed) and that you are logged into your PC as a user that normally runs Pegasus Mail.