I tell you right from the start you most likely won't be able to get it going either. This is due to it being a physical addon device. The same went for and dvd burning program or tv tuner card used here so far with the "fail to initialize device" type errors being seen.
Video and sound
drivers won't go on either while the VPC will still use the virtual video card, see the ATI catalyt go on however, and even access the working sound already setup in 7. While still providing access to all physical drives on the system the mode is primarilry geared for softwares(desktop apps, MS Office, etc.) that you would normally run on XP but is no longer compatible with 7.
Who benefits the most? That would mainly be businesses and professionals who are still relying on XP for things the compatibility mode in 7 itself won't cover for some reason. Yet you can download and install all XP updates since those are Windows related! IE 8 is on the XP mode here.