The only drawback to MemTest (and most software memory testers) is that it can't pinpoint which memory chip is bad. But if you're looking for a memory tester that can be run while Windows itself is running, MemTest is your tool.
Jack Wallen is an award-winning writer for TechRepublic and Linux.com. He’s an avid promoter of open source and the voice of The Android Expert. For more news about Jack Wallen, visit his website getjackd.net.