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:

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
select Check for problems the next time I start my computer