I am not sure if the 300W HP PS could run 9800GT, but I do know my Dell 300W PS has run a 512 mb HD4670 for the past year with no issues. Not a heavily loaded system, C2D 7300, 1 SATA HD, 1 DVD-RW, 3 gb of ram. Kind of depends on what else is in the box, multiple cores CPU, 4 sticks of ram, multiple DVD drives and many fans may be a bit much for even a 4670 with a 300W PSU. I just installed a Corsair 400W unit in a relative's HP to make sure the new HD4670 I got for them wouldn't have any issues. That system is an E6600 Quad, with 8 gb of ram and 2 hard drives. Figured it should have a safety margin, so I threw in the PSU along with the vid card. Hope it helps their 4 boys have a merrier Christmas.