[Relates to all operating systems]

FREE Memory Tester:

Needing to diagnose your system's RAM, be it desktop or notebook?
Want to know compatibility between installed pieces of RAM from different manufacturers?

Here's the one I use:
Memtest 86+, released 2/15/2005

Here's the direct download for the floppy version (DOS-WIN):

Here's the direct download for the USB Key version (Pure DOS):

Here's the direct download for the Linux version (.gz):

Here's the direct download for the CD ISO image:

For the floppy version, it makes a non-readable (Linux based) bootable floppy which you will use for your bootup. It tests automatically once booted from.

In case you need an installation tutorial for Memtest86+ go here: http://www.short-media.com/review.php?r=276

Hope this helps someone.