Sorry about not replying sooner. (Lost all my passwords...)
almatic: how would I go about doing that?
MGorsky22: No offence, but I think I will stay using KDE.
Well, it did work on the other PC.
EDIT: Never mind... I figured out how to switch 'sync to vblank' off.
I also got the official nVidia drivers from the website.
Now Beryl does not give me a white screen.
Unfortunately, it also doesn't give me the effects.
Ah well. It's not vital, I'll just have to do without it.