Virtual PC uses a S3 Trio for emulation.
I've yet to find a DOS game that doesn't work under any Virtual machine that supports running MS-DOS. I have a S3 Trio (the exact same one implemented by Virtual PC) and I can tell you, any problems games have on Virtual PC are the same as they would be with the actual card... I'm looking at you, scorched earth... (That may be what you were saying Dave but I read it like you meant that the problem stemmed from the fact that there was virtualization at work)
Also, as for "DOS 7.1" there are a few points I would like to make:
-the installer says it's "GNU Software". It's not. it's the same DOS, they just ripped it out of Windows 98/98SE and added a crapload of other stuff. It's still proprietary. You can't just slap a "This is GNU Software" on top of something already licensed in another way and say it's legal.
-because of the aforementioned reason, it is technically illegal to download and use it if you don't have a proper license for Windows 9x.
-I'm pretty sure posting links that are "borderline" in this way <might> be against the forum rules.
-What does this DOS 7.1 have over freeDOS? not much, really, at list with regards to running older games. Probably easier to get booting from a flash drive as well, additionally, freeDOS is actually free and there is no question or "gray area" or legal BS to try to comprehend with it (with the exception of the GPL, I suppose (is freeDOS GPL?), which is a rant in and of itself)