How to Test System Memory

A handy tool for testing system memory is Memtest86+ Advanced Memory Diagnostics Tool.

This tool will test memory and help diagnose which memory module is faulty.

the tool can be downloaded from: http://memtest.org/#downiso

Windows Vista has a built in Memory Diagnostics Tool
To use the Vista Windows Memory Diagnostics Tool:

Click the Start Button
type Memory in the search box and press enter
click on Memory Diagnostics Tool
select Restart now and check for problems
-OR-
select Check for problems the next time I start my computer