I’ve been using Memtest86 and its successor Memtest86+ for so long now, it’s hard to remember when I started; a decade ago to be sure. Memtest86+, as you might guess from the moniker, is a memory checking program that runs a battery of memory tests including random numbers, moving inversions, bulk writes, etc. What you might not guess is that it’s free/donationware.
I’ve used Memtest86+ on literally hundreds of PCs, both for memory and CPU burn-in and tracking down memory issues (which generally present themselves mysteriously as blue screens and random lockups). It’s never failed to find a memory problem. It even shows you the problem addresses so you can determine which module is at fault.
Memtest86+ downloads as a 70KB zip file that expands to about a 2MB .iso and no, that’s not a typo–it’s lightweight and then some. Burn it to CD, boot it, watch it, and that’s it. There’s also a version for floppy and one that will install on a USB thumb drive–both equally as small.
Memtest86+ is so useful, it’s even included on the Parted Magic and Slax Linux boot discs to troubleshoot what might appear to be installation issues. It’s an absolute must-have for any PC toolbox. The team accepts donations so throw a couple of bucks their way if you get a chance.