Why isn't he just using an AGP card? Gee, PCI is worse than AGP (graphic cards only, though). No wonder he gets problems.

Anyway... Is it put in properly? That's the first thing you have to check. A lot of people make that mistake.

Secondly, does it have enough power and is it compatible with his computer?

Finally, if none of above work, try the following:
- Move it to a different PCI slot.
- Make sure it's not sharing too much IRQ bandwidths (PCI cards tend to do that a lot, because the data transfer is less effective than that of an AGP card). Leave it on one IRQ if possible. The maximum is one IRQ every two PCI cards (more is possible, but not recommended).
- Get rid of the PCI card and get an AGP one.