Consider a Dell Dimension E310 that powers up but will not boot. No video signal gets to the monitor. Diag lights 3 and 4 on the front are lit. That code indicates a memory problem.
I've tried replacing memory and clearing CMOS and unplugging devices etc but without success. I'm about to declare it a failed motherboard but I thought I'd ask if anyone has any other ideas?
I did clean a massive amount of dust from the cpu fan / heatsink but it didn't help.