I have a fairly new homemade PC and I've been having a lot of things go wrong with it.
Just recently, I had to replace the motherboard (ASUS K8N-VM) because the old one didn't have a functioning PCIe slot. The replacement is the exact same make of board as the old one.

After I replaced the motherboard I was having problems with the MEMORY (or that was what asus support told me) because the computer was crashing as soon as I tried to run any programs. I was told by asus support to set the ram speeds manually, and I did, which seemed to help. but then it got worse.

Right now the computer crashes whenever I try to boot up, before I get to the desktop. I did a completely fresh install of windows 2000 and I ended up on the desktop, but when I put in the motherboard drivers (ethernet, sound, etc) and restarted I was unable to get to the desktop. This isn't a problem if I boot up is safe MODE, but it is a problem even if I use another harddrive. I've checked the cpu temp in the bios after a crash and it is usually around 39 C (80 F), so I don't think it is that.

Is this still a memory problem?
Does anyone have any other suggestions?Does the other HDD happen to have an OS installed on it ? ? ? If so leave it out of the equation for now til we narrow down the issues.
I would first re-set the BIOS back to it's default settings...i can't see a board manuf. asking you to mess with memory timings to troubleshoot but hey...i've heard it all.
DLoad and run MemTest and let it run for a few hours....
It runs from a bootable floppy/CD so Windows is not necessary.
Also DLoad and run the HDD diagnostics from the master HDD's manuf. site...these are free.
Report back with your results.HDDs: both hard drives have win2k on them and were BOOTING happily before I replaced the mobo. I have tried booting with both together and seperately. I now just have one in. I'd assume that this means the problem isn't with the harddrives. but I haven't done the diagnostic for them yet.

I am doing the memtest now. The first pass didn't seem to result in any errors, at least the errors colume is still at zero and there are no flashing red danger signs (I don't know how it actually reports errors...).

I was surprised as well by asus saying I had to mess with memory timings. it's the exact same mobo...
setting the clock speeds manually did help though, at least while I was able to make it to the desktop.Leave only one HDD in for now...I have been looking through a couple other forums and problems with power supplies sound vaugly similar to my problems. Most psupply issues sound like they can get to desktop and run programs before crashes at random intervals. My computer always reboots itself during windows startup (around where you enter password).
Thoughts?
Borrow a PSU of the same wattage or greater and swap it in to see if the situation improves...

I would still finish the MemTest though...Memtest went through 2 passes (full cycles) and didn't come up with anything. I have it running again now. How does one know if it finds an error?

as for power supply, I'll see what I can do. the entire system was working fine before the mobo replacement though, and I don't see what I could have done to damage the PSU...can memory still be a problem if there is no problem in safe mode?It can be, but if Memtest found nothing I would move to step two which is try another PSU. You may also want to remove ALL ADD in cards (EXCEPT video if required) and see if that improves things. I have no add in cards, video is integrated.

I went and disconected everything unimportant (dvd drive, second hard drives) from the psu to see if the power supply was the problem. and I formatted the hard drive and reinstalled windows 2k, service pack 4, and some mobo drivers (audio, ethernet, etc.) seems to be working fine, though it did crash once while installing some of the drivers it worked the second time round. now it just crashes and restarts whenever I try to access the internet.

So far:
+I'm fairly sure it's not the hard drive (I have 2 and I swapped them out to check.)
+I'm sure its not the software/os (I've formatted and reinstalled several times)
+I don't think its the ram (ran memtest 86+ and 4 passes found nothing wrong)
    The ram was a problem before, I had to manually set the timings for it, seems fine now.
+I don't think it's the cpu. I don't see how this can only partially fail.
+It might be the power supply, but it was working fine before I replaced the mobo, and it only has a floppy, a mobo, a cd drive, and a sata hard drive running off it right now (400W no brand name that I can see on it, I think it's second hand). and the computer seems to run fine right now except of internet.
+The mobo is a replacement from the manufacturer and was supposedly tested before they sent it to me. Perhaps I missed connecting something correctly? I don't see how that could be a partial problem...

Thanks for all your help so far. Quote

(400W no brand name that I can see on it, I think it's second hand).