If your webcam is new, I assume it came with an installation CD. If so, pop it in and follow the instructions. If not, go to the camera's manufacturer website and search for drivers for Windows 7. If there are no drivers for Windows 7, you can try Vista drivers.
Let us know if you were able to get it installed!
Cheers, Cassandra Microsoft Windows Outreach
Cassandra, how cool would it be if your last name was "Winteam" AND you work for windows! LOL, i'm not going to lie, i looked at your display name real quick and thought that was your last name... long day, good talk.
chances are, her webcam is not supported. Then windows xp mode can be tried, but easier to buy a new one that actually works under win7.