PROBLEM.IS IT MOBO OR PROCESSOR?

i have a 3.0 Ghz LGA775 P4 on a 915g gigabyte motherboard. i started it and it was loading windows xp. at the windows xp startup logo suddenly the monitor went black and cpu turned off. I pressed the power button again but nothing happens not even a beep. I thought it was psu prob but i checked it on another p4 (socket 478) machine and it worked. then i put another psu and now i hear cracking sound from the fan and the power led turns on but dim. nothing appears on the monitor.

which could possibly have prob, mobo or processor? thanks for any help.

Check your heatsink. Make sure its on securly. Since the PC boots, most likely the processor is overheating.

the pc does not boot. with the original psu nothing happens. with another psu it gives cracking sound, the power led turns on but dim and nothing happens on monitor. both psu works fine on a p4 socket 478.

the 4 pin atx 12v p4 power cord turns hot however in a second.

oh also, i had the same problem (but with an athlon 64) where it did not boot at all! (turned out the motherboard got fried) and then later down the road the CPU died.

So do this: 1. check the CPU or mobo on different parts if at all possible.
2. if above is not possible, RMA your motherboard then when it gets back see if everything works. and if everything does work then you're all good!