I think I fried my processor and possibly motherboard. When I try to boot the computer it makes some whirring sounds for the fan and the hard drive but nothing outputs to the screen. The keyboard is not being read so I suspect I fried my processor. What would cause this? I don't think I disconnected the fan or anything. I did install some new memory recently - a 512 stick PC2700 to go with some 256 sticks of PC2100. I assumed the new mem would be backward compatable. I've already ordered my new processor. My question is whether or not installing a new processor on a motherboard that may or may not be fried is dangerous. Or, is there any way to check if the mb is fried? Or, finally, any good quick way to check if the power supply is the problem? Thanks for any suggestions.

Why would you order a new processor if you're not even sure what the problem is?

It could be the psu Unplug everything but one stick of ram, the vid card (a cheap one if you have it), and the cpu. Keep the monitor and keyboard plugged in, fans, and nothing else. See if it will give you a post screen. If so, put everything back in one at a time, booting in between.

The best thing to do is take things step-by-step. If all that you have done is add more RAM and then it stopped working, that would be the first place to start. Just like John said, the first thing to do is keep only 1 stick of RAM in, and then try booting. If you try changing 3 things at once you are not getting to the source of the problem. My other guess is that you might have done something to the IDE cables that connect the HD/CD-ROM to the motherboard, so maybe just check all your connections to see that they are tight.

I had the same problem of nothing coming up on the screen, but the fans ran. I waited awhile and nothing. You could have fried the MB, I didn't think I did until I grabbed a flashlight and checked the MB very carefully from top to bottom, and I found the problem, it did fry and it was just a little part of the MB near the agp card slot,you could hardly even see it, all it takes is a little to render your MB useless, check carefully to see if its not fried.

I have tried reducing to the min8imum components. MB, CPU, 1 stick RAM, and Vid Card. I don't get anything. I've swapped MB's with one I've known too work - that gave nothing, I've swapped Vid Cards too. The processor had a black filmy liquid on the non-pin side suggesting bad things. Is there any way to know if it's the PS with a quick check (not having another PS available).