MemTest is a RAM tester running under Windows. It tests whether your computer can reliably store and retrieve data from memory. A properly functioning computer should do this with 100% accuracy, day in and day out. A computer that fails these tests, perhaps due to old hardware, damaged hardware, or poorly configured hardware, will be less stable and will crash more often. Worse, it will become even less stable over time as corrupted data is written to your hard drive.