I stay away from ATI myself too. I think that ATI produces technically better hardware than NVidia, but at the same time that their drivers are much worse. I have friends in the game industry who have lots of experience of NVidia vs ATI issues on compatibility etc. and they share this opinion too.
Wanderer, I use a GT 240 on Windows 7 64-bit without any crashes or problems whatsoever. Try changing the IRQ assignment settings in the BIOS, that has always got rid of random HW related crashes for me.