You both should download drivers from your GPU manufaturers site. Yes, I know that there's automatic update in Windows 7, but it only downloads DirectX drivers (wich most games use). BUT Toribash uses OpenGL instead of DirectX (Why? Because it's multi platform game I.E it's made for Windows, Linux and Mac.

Here is tutorial for installing drivers.

I felt no drop from XP to 7 Ultimate. I did update my drivers right away.

Note: there is no performance drop that is recognisable from XP to windows 7, make sure your drivers are installed correctly, measured drops from XP to windows 7 turn up about 1fps difference in games.

Update drivers

It was the opposite for me it ran badly on XP and now works perfect on 7 ultimate

windows seven is slower
it takes up more space

I will state this again, I've read technical articles on the speed difference between vista, 7 and XP, and none of them have any specific speed advantage, they come out on top in different orders seemingly randomly.

[EDIT] This isn't the exact article i was referencing (I can't link you to a magazine page xD) but this will do fine:
http://www.pcmag.com/article2/0,2817,2355703,00.asp
apart from start up time windows 7 appears to be faster, vista lags behind allot but not by anything noticeably bad.

If you score 1 for average, 2 for green, and 0 for red:
7: 9 points
XP: 6 points
Vista: 3 points

Listen to Vox. He is a support moderator and knows what he is talking about.