Any tips for improving gaming performance in XP?

I have XP SP2 installed on my iMac (2ghz), which is maxed out on RAM at 2GB. Since it’s an iMac, a video card upgrade is not an option.

I only have XP installed for gaming (via Boot Camp). Is there any software/OS tweaks to boost gaming performance?

P.S. I haven’t installed any of the system updates since I wasn’t sure if they’d do more harm than good.