me wrote:
to test the RAM in a PC?

www.memtest86.com (MemTest86)
www.memtest.org (new version of MemTest86, called MemTest86+)
www.goldmemory.cz (Gold Memory)

Use both Gold Memory AND MemTest86 (or MemTest86+ for newer modules and
mobos) because I've had modules that passed one for several hours but
not the other. Run each one overnight, preferrably in more than one
memory slot and more than one mobo.

He http://www.realworldtech.com/page.cf...WT120901222920
is an evaluation of several memory diagnostics, and they found
MemTest86 and Gold Memory to be among the best, with only the products
from Ultra-X (not the power supply company) being better. OTOH some
other diagnostics were outright lousy, like DocMem from SimmTester.com,
which I've found will pass almost anything.