memtest86+

download, burn, boot from the disk, test!

something else you could  do is find a program that can check the S.M.A.R.T. status of your hdd's. SpeedFan can do this as well as  monitor your temps and fan RPM's. its good  to have a copy of it anyway. once its installed  go to the S.M.A.R.T. tab, select your drive from the dropdown lits at the top and it will tell you how healthy the selected hard drive is as well as its performance.