Did you know that random BSOD (Blue Screen of Death) errors can be caused by a failing hard drive? If you suspect your hard drive is on the way out, be sure to back up your files. A standard hard drive’s likelihood of mechanical failure goes up significantly at 4 years old.
If you are having BSOD errors and have ruled out other usual suspects (viruses, spyware and software), it may be time to consider hardware failure. There are many free hard drive testing programs available.
The native Windows program provides a rudimentary check, but cannot examine the physical state of the hard drive. (right click hard drive → properties → tools → error-checking).
For a more in depth physical check, I recommend Seatools by Seagate (FREE and works on any brand hard drive). http://www.seagate.com/support/downloads/seatools/