Re: Dell computer help
Go with the Radeon 9250. I have it and does wonders for people who don't have agp/pci express slots. I believe it can handle Doom 3 and Half Life 2 on decent settings, with minimal lag. Your celeron may be the problem here. It's just not made for gaming.
Rig -- Emachines T5026, 3.06ghz P4, 300W Bestec PSU, 160 sata hd, 512mb dual channel 3200 ram @ 3-3-5-8, ATI Radeon 9250 pci, dual layer 16x dvd+/-rw.