My friend's HP Pavilion a720n has been giving us headaches for weeks. We installed a Radeon 9800 Pro 128MB, which overheated (we bought an ATI Silencer) and was not getting enough power (we bought this FSP Fortron on the recommendation of [H]ardForum's PSU sticky). Now, as far as I can tell, we are back at square one....boo.
System Specs:
Athlon XP 3200 @ 2.2GHz
512MB DDR333 (the memory module is actually a PC3200 when I looked)
VIA KM400A Chipset and Motherboard
Radeon 9800Pro 128MB AGP 8x
No PCI cards installed
Onboard sound
USB mouse
PS2 keyboard
350w FSP Fortron PSU
DVD Writer/CD writer
CD-ROM drive
9-in-1 reader

System Specs:
Athlon XP 3200 @ 2.2GHz
512MB DDR333 (the memory module is actually a PC3200 when I looked)
VIA KM400A Chipset and Motherboard
Radeon 9800Pro 128MB AGP 8x
No PCI cards installed
Onboard sound
USB mouse
PS2 keyboard
350w FSP Fortron PSU
DVD Writer/CD writer
CD-ROM drive
9-in-1 reader