Windows Vista includes several new and updated diagnostic utilities. Vista now includes a built-in a memory diagnostic utility, in previous versions of the OS you had to download this utility separately and create a boot disk or CD.
If Vista detects a problem with your computer's RAM, it will automatically display a notification asking if you want Vista to try to detect if there is a problem. You can also manually run this utility anytime by running "MDSCHED.EXE" (which is located in the %SystemRoot%\System32\ directory) from the command prompt, or from the Search bar under the Start menu.
Note: You will have to reboot your computer to utilize this utility.