Windows Vista and Windows 7 have a built-in utility that can check for problems with the computer’s memory. Although the Windows Memory Diagnostic tool often kicks in automatically when it senses an issue, you can also run if manually if the computer is behaving erratically and you suspect the memory chips might be involved.
To use the utility, go to the search box in the Start menu, type in mdsched.exe and hit the Enter key. In the box that appears, you can choose to run the memory utility right then with a restart — or the next time you restart the PC. When the computer restarts, the Windows Memory Diagnostic tool kicks into action. If the program confirms an issue with the memory, you can replace it or take the computer into a repair shop for professional help. Microsoft has more on using the memory tool here.
Taken from this article.