With Windows 7, Click Start button and type 'mdsched.exe' without the quotes in the Search box.
If you choose to restart your computer and run the tool immediately, make sure that you save your work and close all of your running programs. The Memory Diagnostics Tool will run automatically when you restart Windows. It might take several minutes for the tool to finish checking your computer's memory. Once the test is completed, Windows will restart automatically. If the tool detects errors, you should contact your computer manufacturer for information about fixing them, since memory errors usually indicate a problem with the memory chips in your computer or other hardware problem.