The only reliable way to test the Memory in a Computer is to use a utility called Memtest 86+
If you do a Google search for Memtest 86+ and follow the instructions on making a bootable disk.
You boot your PC or Laptop up from the Memtest 86+ disk and it runs a series of exhaustive tests.
If the memory is faulty it will tell you.
It is extremely reliable.
Many instability problems are caused by unstable or faulty RAM, especially home built PC using OEM memory.