My wife has an HP box that was running an Athlon XP 1.4 ghz, with a video card upgrade and 512 MB RAM. One day we booted it up and it was running slow. Real slow. 15 minutes on the splash screen slow. I rebooted a few times, but nothing. OK. I pop it open, make sure everything is connected properly. It is. I pull the CPU. When I take off the HS it takes a chunk of Athlon with it. Huh. I get a new CPU off ebay, that's $35, nothing major. Pop it in. Boot up and... nothing. The keyboard flashes once, then is unresponsive, the display doesn't even attempt to light up, in either graphics port. I look at the back. The PSU's fan isn't spinning, nor is the case fan- however the CPU fan is. Any ideas as to how I can bring back this big bad mammer-jammer? Oh, and the hard drive spins too. In fact, all of the drives respond. I don't think it's even hitting POST. Do you think it's the PSU or the MoBo? Or am I just too damaged in the head to operate small machinery?The easiest diagnosis at this point would be to borrow a known working PSU of the same or greater wattage and swap it in there to see if it is the culprit...

If you do replace it DON'T BUY a twenty dollar one...I have another HP box- actually the case style is identical, the only difference would be that everything inside is older . I think it's got a P3, I'm not sure how much the variance is between early 2000's factory HP power supplies. The biggest problem I'm looking at is that I've never replaced a PSU before. Actually, that's the SECOND biggest problem. The biggest would be the thunderstorm outside...Ok, 35 minutes and one over-sized PSU later... Nothing. At least now the PSU fan kicks in along with the processor. I found an old PSU in my old P3 450 box, but the thing is so big, the HP's CDRW & DVD don't go all the way into the case anymore. Not that aesthetics matter when the son-of-a-hamster won't boot. It's only pushing 50 more watts. I'm not very good at diagnosing hardware problems.

I hear the usual boot up whirs and clicks- no beeps. All the drives do their thing. The keyboard flashes at boot. After about 15 seconds it just makes an idle background whirring. The monitor displays it's usual "plug-me-into-something-I've-been-sitting-on-this-desk-for-a-year-and-a-half-and-I'm-bored"
message. Would it work better outside in the rain, perhaps? Seriously, though, I need this box up and running. My wife can't play her Sims (it crashes on my computer every 3 minutes- but it can play Half-Life 2, go figure?) and she reminds me of this fact every, oh, 5 clock cycles or so.Remove the video card and try it with the onboard video...Ok, tried it with onboard to no avail. Activity light is ACTIVE for the first 5 seconds or so then goes out. One of the fans is STILL not kicking in. Maybe an exorcism?A bench test would be better.

Remove all components from the case.
On a rubber mat or a piece of cardboard hook up only the following:
PSU
CPU
MBoard
Vid Card
1 stick of RAM
Mouse
Keyboard
Monitor.

Re-boot and see if it posts. If it does add only one component at a time to find the culprit.
Remember to take this opportunity to thoroughly clean out all components with a can of compressed air. Use a QTip to hold the fan blades in place when blasting them...Ugh, this'll be a fun one. Oh well, you wouldn't be a mod if you didn't have some idea of what to do. I'll be back later to describe it in all of it's gory detail. Hopefully it SURVIVES surgery... If it doesn't make POST I'm to assume it's the big one, right? That big Mobo heaven in the dumpst- er sky?