Tried searching this, but I wasn't sure what to put in.
I've just installed and updated xubuntu 8.04 on a junker I put together. 2.0Ghz Celeron, 440MB RAM. I'm getting artifacts on the screen, and it bogs down terribly on youtube videos. It will run at full resolution, however. (the desktop, not youtube)
If this helps:
I still get artifacts in the BIOS splash screen
It's a 128MB card, AGP slot
The motherboard is from an HP Pavilion, and has no onboard video
Nothing should be overheating...there are 3 chassis fans, plus the ones on the ATI, the CPU, and the power supply.
Everything else seems to be fine. The cpu is a bit sluggish but works fine, and I'm well within my RAM limits.