Shut down the computer
Unplug the power cable
Open the case or access the RAM compartment
Reseat the RAM sticks
Boot into the BIOS or UEFI and check if all RAM is detected
Run Windows Memory Diagnostic
Run MemTest86 from a bootable USB
Let the memory test complete all passes
Check for errors, crashes, freezes, or reboot loops
Test each RAM stick individually
Test each RAM slot individually
Replace any RAM stick that shows errors
Replace any slot or motherboard component that fails with known-good RAM