There’s no need to sit and watch the test as the results will be saved for you. A dialog balloon will appear on your task bar when you boot to tell you what happened, or you can check yourself through the Event Logs. Right click My Computer, choose Manage, the Event Viewer, System. The test logs will appear under MemoryDiagnosticResults with the ID of 1201.
If you do decide to watch the test and the test reports no errors, then the memory is probably fine. To be sure, the tool runs two passes just to make sure. If the tool does find errors it will display the error type and where the error occurred.
If you are experiencing problems like errors on booting, crashing, program errors and the like, then memory may be an issue. This is where this tool comes into its own. When you are getting memory errors, the memory diagnostic test results will tell you which slot the error is occurring, so make a note of it. Turn off the computer and swap the memory around so a different stick is in each slot on your motherboard. Run the test again and check the results. If the test now says the fault is in a different slot then chances are the problem is with the memory. If the test reports the same fault in the same slot, then the problem is probably with the slot or the motherboard. You can try cleaning the slot and running the test again just to make sure.
The Windows Memory Diagnostic Tool is a good first step in troubleshooting memory problems and has been found to be very reliable. Using it when experiencing system problems is a good way of troubleshooting, and hopefully will resolve the issue.