My wife was crashing occasionally, I think we fixed the problem by using the latest Omega drivers for her ATI 9700.
Her specs
AMD XP 3000+
Windows XP home SP2
1 gig PC 3200 ram
ATI 9700 128meg Radeon Omega Drivers 2.6.05a (Catalyst 5.1)
www.omegadrivers.net
She still has some graphical glitches from time to time, but no crashes since the driver update.
Make sure you uninstall ALL ATI software from your PC before you install the new drivers.
Good luck.