Do a standard diagnostic test. In this case it will be Memtest on your RAM. The beauty of this test is it starts the second you boot up.
See the link below and follow the instructions. There is a newer version than is listed but either one should work. If you need to see what the Memtest screen looks like go to reply #21. The third screen is the Memtest screen.
Let it run for a LONG time. The rule is a minimum of 7 Passes; the more Passes after 7 so much the better. There are 8 individual tests per Pass. Many people will start this test before going to bed and check it the next day.
If you have errors you have corrupted memory and it needs to be replaced.
Also, with errors you need to run this test per stick of RAM. Take out one and run the test. Then take that one out and put the other in and run the test. If you start getting errors before 7 Passes you know that stick is corrupted and you don’t need to run the test any further on that stick.
Link: Tutorial:
http://www.techspot.com/vb/topic62524.html
* Get back to us with the results.