Windows memory (RAM) testing tool from Microsoft

RAM (Random Access Memory) is one of the most problematic components in a computer. For example shut down or rebooting while booting, unexpected restart, disappearing applications, operating system doesn’t install, no display, etc may happen because of memory problems. if you have experienced any such problems while running your Windows operating system, you can use Windows memory diagnostic tool to test it. The Windows Memory Diagnostic tool includes a comprehensive set of memory tests and determines whether the problems are caused by failing hardware, such as RAM or the memory system of your motherboard
The application FREE and is designed to be easy and fast. On most configurations, you can download the diagnostic, read the documentation, before running the software and run the test. To run Windows Memory Diagnostic, you must reboot your computer with the disk or CD-ROM on which you installed Windows Memory Diagnostic in the drive. After the reboot, Windows Memory Diagnostic will load and its interface will appear.
After loading, the first test pass will begin, using the default standard test suite, and continue until complete, unless Windows Memory Diagnostic is either paused or exited. Once the first test pass is complete, Windows Memory Diagnostic will begin a second test pass using the same settings as before. Windows Memory Diagnostic will continue to run test passes until you exit.[via – askvg]
Download Memory diagnostic tool