First time I've ever seen memtest return an error...
My attic-ware is falling apart. It uses ye olde DDR memory.Can I deduce from the memory address memtest reported which module has a fault on it? Is there a sane way to find out the module in question? There are three modules, and I hope only one has errors.
[Found this: http://www.hcidesign.com/memtest/support.html]
I'm not sure I have spare modules left. I'm sure I have no money left Darnit. After trying to find the error for several days, I'll actually give the technical part (and myself) a rest now. I'll have to consider other options... So if anyone has a funny suggestion, try me

I think I have 512 (or maybe 768MB?) of DDR I don't use. Came with the motherboard Matthew sent me... if it's the right type you can have it .

You can tell which stick is bad by testing each one separately.

Thanks for the replies, and thanks for the offer, Trent.
I'm thinking of reinstalling the OS'es as system files may be compromised. (E.g. I had a Linux header file that was corrupted.) Is this a sensible thing to do? You think I can I still activate Windows XP on-line?
I'm purposely postponing the actual testing till tomorrow. I have no DDR-1 left. The PC will suck with 256M less (so let's hope it's 128M ). One option would be to buy a "new" mobo with CPU-onboard for about 50 euro. Nice and power-saving >_>
I'm gonna have a look at second hand PC's now.

Just memtest the existing sticks one at a time. No reason to postpone that.

Yeah, there was
I've found the faulty module. Also I've ordered some second-hand modules for 5 bucks in total. Not too expensive.
I tried booting up now, but apparently I don't have reconnected the hard-drives properly.
Reinstalling everything might be too tedious to bother.
Hm, this PC is giving random program crashes too in Linux... Maybe I should memcheck it too.

I don't see why. Running the system with faulty modules is asking for trouble, so its either going to be sitting turned off, or running those memtest86+ checks for you. See? No need to wait