You can test your hard drive and memory free; go Here and download Seatools for DOS (free) ISO and burn it to a CD. Make sure your BIOS is set to 1st boot device = CD drive; reboot with it in your CD drive, and when the screen appears choose the short test at the upper left corner. Let it run until it posts "test complete", about 20 minutes or so. At the end of the run it will give you "pass" or "fail" message; or, If it messages you that SMART is tripped, that means the drive is bad.
For a memory test, I have the following canned post:
Download Memtest 86+ , the "precompiled Bootable ISO (zip)" file (free) from my link; burn it to a CD. Be sure your BIOS is set to CD=1st boot device, Hard Drive=2nd boot device; reboot with the CD in your DVD drive. You will see the screen appear and the testing will automatically start. When it has completed all the tests, the message "press key to exit" will appear. Any errors found will be listed, even one error means that stick of memory is bad. I suggest testing each stick separately if you have more than one installed.