Windows 7 - PC freezes - HDD light constantly on

I've noticed that at random times my PC freezes and becomes unresponsive (the mouse moves though). The HDD light stays on and this all lasts for around 20 seconds sometimes longer.

I have Windows 7 Pro and disabled indexing and superfetch. I opened system monitor and when the freezing happens I dont see any changes in there. The hard drive is about 3 years old, could it be dying? My hard drive has only got 8MB cache could that be the culprit?

Here's the results of Crystalreports: ImageShack® - Online Photo and Video Hosting

Any help would be greatly appreciated

Probably not the HD but a check disk would tell you. I suspect it is just writing to disk. I am unsure as to what apps you have installed or how you use them but 4 gigs of ram on win 7 64 bit isnt a ton and if you have HD apps like photoshop, or video editing apps writing may be it.

8Mb cache? cpou, HD, other???

I have a ran a checkdisk which came back clear. It doesn't matter if I have just Firefox open browsing the Internet, or multiple applications open at the same time the freezing happens at random times. The 8MB cache refers to the cache on the hard drive.

Not sure what could be causing this? I've had the same installation of Windows for over a year now, does it need formatting and re-installing?