Hi Greg,
what i'm saying is not related to OS but to Xpedition VX.
In my desktop with Win7 Pro 64bit, I have installed EE7.9.4 and Xpedition VX 32bit under same root "C:\MentorGraphics".
It works without any issues for about a year when was released Xpedition VX.1
This installation follows MentorGraphics specifications.
Best Regards,
Bortolo