A couple of things going on here. First, a lot of systems seem to crash on Nature and the High Polygon tests in 3dmark2001. Uncheck these and see if the test completes. I could never get these tests to complete when the OS was Me. But when I installed Win2KPro, they would run. If you can get 3DMark2003 to complete without running Nature and the High Polygon tests, and you can run Prime95 successfully (see below), then I wouldn't worry about the crashes.
The artifacts may mean that you were one of the unfortunate to get a 9500 which will not successfully patch with Soft9700. OTOH, it might mean be the combined result of your patching and your overclocking, and that you'll need to back down on your overclocking.
What kind of stability testing did you do when settling on your overclock? Can you run the Prime95 torture test at your overclock without the test failing? Others have recommended that you try default settings (e.g. no overclocking). If you haven't run Prime95, or some other good "burnin" program, I'd try that, to see if the problem is the overclocking.