I bought a case and motherboard combo GX520 SFF. The unit was new. It has some scratches so it was rejected by Dell. Anyway, I hooked everything up, DVD,80GB Sata HD, 512 DDR2 Ram etc.... I put in a celeron D chip, 3.46Ghz, and the system wont go past the opening bios page that says Alert! System Halted. Incompatable processor. I bought the chip from newegg brand new. I thought maybe it would boot up with a smaller chip that I have in my sisters GX520 "that I built" a Celeron D 2.66Ghz chip. I know these work in the GX 520s. But still I get the same alert. What can I do? It starts with system setup in green letters, then the alert after right away. Anyone know what I can do????? I've tried removing jumpers and battery and disconnecting everything from the mobo but the memory and processor with heatsink same warning with either chip. My niece has a gx620 MT with a 3.33 Celeron D chip. It works fine and like I said my sisters is the same model 2.66GHz Celeron D I bought. HELP!