I'm fixing a desktop for a friend, after their Windows installation died. Reinstalling windows led to numerous BSODs during installation (IRQL_NOT_LESS_OR_EQUAL being the most common). After finally installing XP again, it worked for a while so I installed SP3. And it died again.
So I decided to test the RAM. My Linux LiveCD had memtest86+ 2.11 on it, so I ran that. It's now at 51% with just under 2 million errors. My laptop passes the test without any problems, so it's not a problem with the memtest on the disc. This presumably means the RAM is very bad, but it was able to run the Linux LiveCD for about an hour to back up the system without any problems.
Is the problem definitely the RAM, or is something deeper wrong? I don't want to advise this friend to buy some more RAM, and then find out that the motherboard is fried.
EDIT: In case it makes any difference, the PC is a Lenovo ThinkCentre A58. It's got a 320GB HDD, and original came with Vista and XP discs, but the Vista disc has been lost.