For the first time I tried to replace the MB and CPU at the same time in a Dell Dimension 5100. The first time I booted, the POST said that the amount of memory has changed and asked me if I wanted to proceed or go to set-up. Stupidly, I chose to proceed and the screen just went black and nothing happened. When I tried rebooting the computer, now all I get is a black screen....no POST...no nothing.
OK, so what do I need to do to get the POST back and proceed with the set-up? Remove and replace the memory again?
Well, I reseated the memory, and pulled the green jumper by the CMOS battery a couple of times. For the first few attempts, I got absolutely nothing, although the LED's on the two optic drives would flash in a rhythmic pattern. (The monitor is plugged into the MB video port.) Now, I am getting a flashing cursor but no indication of the POST running or any reaction to the USB keyboard.
Interestingly, this is the state the original motherboard was producing. Is it possible there is an issue with the power supply?
Then ,just for giggle, I pulled the video and sound cards. Now, it's back to no video and one optic drive just flashes....long, short, long, short, etc.... Any other ideas?
The Dell 5100 can only support P4 CPU (LGA775) with L2 Cache 1M but the one you had which has the L2 Cache 2M, that why your PC can't boot. They are not compatible. You need get the P4 CPU with only L2 Cache 1M.
Unplug power chord, remove ram cards, remove CMOS battery for 10-20mins replug the power chord.
No need to remove the battery for more than maybe 20 seconds. Just need to start counting from after the 5VSB LED has gone out after unplugging the PSU, otherwise the CMOS may still be powered by that instead even with the battery removed.
Well, I've installed the original CPU and tried your suggestions of unplugging everything and the CMOS battery, but alas I get the same results....nothing but a flashing cursor and even that takes quite a few seconds to appear.
So, I'm completely stumped. Does anyone know where I might have gone wrong?