Random freezes/crashes with no BSOD or error message

First off my crashes are very random and I can sometimes go a month or 2 between crashes, but the crashes usually occur while refreshing or opening a page while browsing, my PC will freeze with my keyboard & mouse becoming unresponsive, a humming/buzzing sound also comes from my speakers, the buzzing stops after about 10-30 seconds, but my PC remains unresponsive with no BSOD or error message leaving me with no option but to force restart my PC.

I have checked my event viewer and can't find any errors besides the error that the computer did not shutdown correctly, caused by me force restarting.

After looking around the forums this seems to be an issue that pops up on here every once and a while, but it seems that the solution varies from PC to PC, so I don't really know where to start, and with my crashes being as random as they are, it is very hard for me to see if something has fixed the issue or not.

Im hoping that someone can possibly shed a little light on my problem and maybe give me some tests I could run that could pick up what the problem may be.

thanks in advance,
prizna

Work through the Troubleshooting Steps for Windows 7 reporting back results as you go as there may be other steps indicated.

Let us see a screenshot of Disk Management - Post a Screen Capture Image.

Are there any devices in error (with a !) in Device manager?

Enable Automatically deliver drivers via Windows Update (Step 3) then Check for Updates, install all Important and Optional Updates except Bing. After requested restart check again until no more are offered.