Windows Memory Diagnostic is a free utility available for download from Microsoft designed to sniff out flaws in a machine's RAM modules. The fact is that the source of the now ubiquitous blue screen is not always Windows, or any piece of code for that matter. The fault could just as well reside in system memory, and this is where Windows Memory Diagnostic comes in. The tool is capable of evaluating the RAM on a computer and identifying any error.

"Windows Memory Diagnostic supports x86-based computers with the following microprocessors: Intel - Pentium or Celeron families; AMD - K6, Athlon, or Duron families; and microprocessors compatible with those listed above. You can test all types of RAM that run on x86-based computers with the supported microprocessors," reveals Microsoft's description of the tool.

Both Windows Vista and Windows XP users will be able to create bootable media (either a floppy or a CD) which can be used in its turn in order to boot the computer. Windows Vista already features the tool integrated as a default component under Administrative Tools, or accessible via the Repair option in the operating system's installation media. However, Vista offers a slimmed down version, with little visual feedback and less options. Instead, the Windows Memory Diagnostic utility comes with three categories of tests, namely Basic, Standard and Extended. Users can choose between running two tests in Basic mode, six in Standard and 11 in Extended and a scenario which is bound to last at least the entire night.

"However, if you have error checking and correcting (ECC) RAM, Windows Memory Diagnostic may not report any errors because the ECC mechanism automatically detects and corrects the error. It might still be useful to run Windows Memory Diagnostic if you have ECC RAM because it may detect errors that the ECC RAM is unable to correct (which indicates problems with the RAM). Windows Memory Diagnostic is limited to testing only the first 4 gigabytes (GB) of RAM. If you have more than 4 GB of RAM, the remaining RAM after the first 4 GB will not be tested by Windows Memory Diagnostic," Microsoft added.

Microsoft Windows Memory Diagnostic is available for download here.