This PC has an ASUS motherboard, AMD Athlon 2400+ CPU, 80Gb HDD, CD-RW, CD-R and FDD and 256Mb RAM - manufactured by Carrera approximately 15 months ago.

Last night the 300W PSU blew.

I have installed a new 500W replacement unit. The PC was able to boot into XP Home but then powered off - it was unable to detect the HDD, FDD or either CD from explorer. When booted into safe mode with command prompt or booted from DOS the PC was stable. chkdsk shows that the C: drive has a corrupt bitmap index on the MFT.

I have enabled the POST RAM test which passed. I have also tested the RAM using a MemTest86 - this detected errors all over the 256Mb RAM. A new replacement DIMM was inserted which also returned errors (I don't believe the results from this test).

My thoughts at this stage are that the Motherboard has been damaged by the PSU failure and this is the cause of the unpredicable behaviour.

You opinions would be appreciated.

Unfortunately there is a good chance you are right and there is a good chance that other components may be screwed too. The only thing to do at this point is to test each component independently of the damaged system....

More likely some component in your system - CD-Rom, burner, floppy drive, video card , LAN card or modem has developed a short and taken out your PSU.

You need to strip back to bare bones - disconnect all drives, remove all extraneous cards - leave only the boot hard drive and video card, then see if you can boot.

Edit: Sorry, I didn't see Budfred's post before I submitted mine.

Just to clarify - I am able to boot BUT the PC dies once booted into windows and it cannot see the HDD's

Yeah, my wife's PC just did the same thing - couldn't see the HD. Turned out to be a Samsung DVD/CD-RW Combo drive. Replaced the drive - booted fine.

There was an existing I/O fault on the CD-RW drive which I was due to investigate.

I have disconnected just this drive and I can now see all the drives using an Explorer window. I guess I need to leave the PC running overnight to check it stays up and running, then remove and replace the CD-RW.

Bad news - after restarting XP with a scheduled chkdsk - the PC died again.

So I guess that I need to disconnect all the drives (apart from C:) and pull all the I/O cards other than the dispay adapter.

I still think the motherboard has been zapped but it is painful to eliminate all the other options.

Has anyone an explanation why the memory test failed even on good new memory if it is a short circuit?

I forgot to mention that the PC does not want to Restart from XP - it siply shuts down.

"I forgot to mention that the PC does not want to Restart from XP - it simply shuts down."

Can you run XP? But then when you restart it shuts down? Tell us exactly what is happening. You may have solved the hardware problem but now have a software glitch.

XP boots up but when you login as one of the users the PC shuts down - sometimes immediately and sometimes after a few minutes.

I also not that I can no longer see the any of the drives with Windows Explorer.

A software glitch would not explain why the memtest86 detects errors on the original and new (error free) memory?

I am going to inspect the motherboard for any visible signs of damage.

Sounds like hardware. Have you tried a bare bones boot yet?

When you look at the MB, pay special attention to the capacitors, the cylindrical thingies on the MB. Look for any signs of swelling. The tops of the caps should be flat not convex.

Bare bones boot works okay BUT it dies as previously reported.

Memory still erroring.

HDD being backed up now in another PC.

I am returning it to Carrera as this sort of thing should not happen after only 15 months.

Well. It's your machine.

I would have tried another stick of RAM just to make sure. But then, I have spare parts laying all over my house - a real computer junkyard.

You are probably right, anyway - that your motherboard is shot, or it could be your video card or HD.

I did try a brand new error free DIMM and MemTest86 reported errors like the original.

Hence my frustration and conclusion.

Let's see what Carrera make of it when I ask for my money back!!

Forgot to say that the Video card is fine as I tested in a Dell but the HDD is odd. The Dell cannot see it from the BIOS setup screen but XP can see it (and I have been able to copy files to archive)? It is an 80Gb EIDE Maxtor.

Well, you've ruled out the video card, and it sounds like you got the HD to work in another machine. All that's left is memory and motherboard.

Try the memory in another machine. Yeah, yeah, I know you have tried replacing the memory with supposedly good sticks.

You can probably replace the Asus motherboard (since it's not too old) with the same model for about $65 at NewEgg. Not sure which one you have though.