How to find Bad Memory In Vista?

Unexpected or chronic system errors can sometimes be caused by faulty RAM. For checking the Vista system’s memory, there is a built-in Memory Diagnostics Tool.
To find the Memory Diagnostics Tool, just type Memory Diagnostics Tool into the Start Search box and then click the tool. Since the Memory Diagnostics Tool can’t check memory while Windows is running, there will be given two options-
Restart the system immediately and run the test, or run it the next time you restart.

The memory test usually takes around 10 to 15 minutes to complete,and when it’s finished, your system will automatically restart and let you know if any problems were found.

Ref: Smart Computing