Freezing, rebooting Win 7

Hi everyone,
I have my PC for about 3 years and I always keep it running.
Recently (it happened once two months ago and again this week), it freezes, the screen goes black, and it shows the blue screen indicating "dumping memory"! Then it restarts and freezes on the start up screen. I need to the turn it OFF and ON manually afterwards.
I am not sure whether this is a problem of the hard drive, power, or something else?
Please advise on this.

More info:
Recently, I hear strange noises from the hard drive. It is like when you copy a file. This noise is not consistent and it happened for a short time during last month.
I got a screen capture of HD Tune health tab window and attached below. I am not familiar with this, so appreciate any help.

Hello si14 and welcome to Seven Forums.

It's possible that your hard drive is failing, especially when you hear noises coming from it. Sometimes a failure is immediate but other times it could be several days, weeks, or months before the drive completely fails. I would suggest backing up your data immediately. Keep in mind that any additional stress testing (which involves reading and writing to the drive) could speed up its failure.

Once you've got your data backed up, you could do additional testing and/or troubleshooting. Western Digital has their own testing tool called "Data Lifeguard Diagnostic for Windows". Or you could use the tools suggested in this troubleshooting tutorial that was prepared by one of the Forum experts.

http://www.sevenforums.com/tutorials/220165-troubleshooting-steps-windows-7-a.html

If you need to replace the hard drive you'll also have to reinstall your operating system and all other programs. You might be interested in doing a clean install that will eliminate factory installed bloatware and give you a better performing machine.

http://www.sevenforums.com/tutorials/219487-clean-reinstall-factory-oem-windows-7-a.html