the celeron 420 is at 1.6 ghz versus 3.0 ghz for the Pentium. I did the replacement because I need a cpu that takes less power. I don't think you could under clock the pentium 4 on the dell bios.
Anyways - the computer will not start with the celeron. the computer powers on but the power light stays orange and the display stays black.
WHat is the reason that the Celeron is incompatible? I'm 99% sure the dell bios A08 would support this processor.
I have the "mini-tower" by the way - there is 5 models of the gx280. I followed the instructions on the online dell user manual for changing the processor. the one step I missed is unplugging the power cord(s) from the motherboard. It's a tight connection and It would not come out.