Check RAM for Errors Using 'Windows Memory Diagnostic'

When Bad RAM Is the Suspect

Faulty RAM produces some of the most confusing symptoms in PC troubleshooting: random Blue Screens with different stop codes each time, applications crashing unpredictably, file corruption that "shouldn't" happen, or a system that only becomes unstable under load. Because a bit flip in memory can corrupt almost anything running through it, the failures rarely point cleanly back to RAM itself. If you've ruled out obvious software causes (driver updates, recent installs) and instability persists, especially after a BSOD citing MEMORY_MANAGEMENT, IRQL_NOT_LESS_OR_EQUAL, or similar memory-related stop codes, testing the physical RAM sticks is the next logical step.

Windows Memory Diagnostic is a built-in tool (no download required) that runs a battery of read/write pattern tests against your RAM outside of the normal Windows environment, since testing memory while Windows itself is actively using it would produce unreliable results.

Step 1: Save Your Work and Launch the Tool

The test requires a restart, so close everything first.

1. Press Win, type Windows Memory Diagnostic, and open it from the search results.
2. Alternatively, press Win + R, type mdsched.exe, and press Enter.

Step 2: Choose When to Run the Test

A dialog offers two options:

• Restart now and check for problems (recommended) — reboots immediately into the diagnostic environment.
• Check for problems the next time I start my computer — schedules the test for your next normal reboot, useful if you're not ready to interrupt your current session.

Step 3: Let the Test Run

The PC reboots into a blue diagnostic screen (a minimal Windows PE-based environment, separate from your normal OS) and begins testing automatically using the Standard test mix by default. A progress bar shows the pass count and percentage complete.

1. Press F1 during the test to open Options if you want to change the test mix.
2. Choose a Test mix: Basic (fastest, fewer test patterns), Standard (default, good balance), or Extended (much more thorough, including tests for less common failure patterns, but can take an hour or more depending on installed RAM capacity).
3. You can also set Pass count higher than the default of 1 for more confidence, though each additional pass roughly doubles total run time.
4. Press F10 to apply changes and continue, or wait for the default Standard test to complete on its own.

Step 4: Reading the Results

The PC reboots back into Windows automatically once testing finishes. Results don't appear immediately on screen — they're written to the Event Log and surfaced via a background task shortly after you log back in, usually within a minute or two as a notification balloon, or you can check manually:

1. Press Win + R, type eventvwr.msc, and press Enter.
2. Navigate to Windows Logs > System.
3. Click Find... (or use the Filter Current Log pane) and search for MemoryDiagnostics-Results as the Event source.
4. Open the matching event; it states clearly whether errors were detected, and if so, generally how many.

If Errors Are Found

1. If you have multiple RAM sticks, remove all but one and re-run the test, then swap in each stick one at a time to isolate exactly which module is faulty. Test each stick in the same physical slot to also rule out a bad motherboard slot rather than the RAM itself.
2. If you have only one stick and errors are confirmed, the module itself is very likely defective and should be replaced — if it's still within warranty, most manufacturers (Corsair, G.Skill, Crucial, Kingston) offer lifetime or multi-year warranties on their RAM and will RMA it.
3. Reseat before replacing. A surprising number of "bad RAM" results trace back to a stick that's simply not fully seated in its slot, especially after moving or opening the case. Power off, unplug, remove and firmly reseat each module (you should hear/feel the retention clips click), and re-run the test before concluding a module is actually defective.

Alternative: MemTest86 for a Second Opinion

Windows Memory Diagnostic is convenient but less thorough than the independent, widely trusted MemTest86 tool, which boots from a USB drive outside Windows entirely and runs a more extensive and battle-tested set of algorithms over a longer default runtime. If Windows Memory Diagnostic comes back clean but you're still seeing memory-pattern instability, download MemTest86 from its official site, write it to a USB drive with the provided imaging tool, and boot from it via your PC's boot menu (commonly F12, F11, or Esc at startup, varying by motherboard manufacturer) for a longer, independent test run.