Computer freezes and makes buzzing noise, no BSOD?

So a few weeks ago I was in Sony Vegas editing a video and suddenly my mouse and keyboard both became unresponsive and a loud buzzing noise started coming out of my speakers. I left it for a few minutes but nothing happened, there was no blue screen of death, no error message,nothing. so the only thing I could do was force a restart.

Over the next few days the problem continued in graphical/CPU intensive programs (such as photoshop, Vegas, fsx, etc), and all I could do was restart. Not once did I see an error message. I did originally think that it was due to an overclocking (4.4 GHz) however I checked my temperatures and they didn't ever peak above 60-70. Neverthelss, I underclocked back to 3.3 but still experienced the problem.

I read online that I should do a clean install of windows so I did that, and up until now I thought the problem was solved. And a couple of minutes ago I was playing age of empires and the computer froze and then The buzzing started again.

Here's video I recorded of the sound: youtube.com/watch?v=JiyAqeuGreU

I'm really clueless to what it could be. Ive reinstalled NVIDIA drivers, cleaned out the registry, reinstalled windows, what can it be?!

I think it might have something to do with my graphics card or drivers or something along those lines, as the problem only occurs when in games or video/picture editing programs. However, my computer and all the components are new (about a month), and I can't think of any possible meddling I couldve done to cause these issues. After all when I first built the pc, I was having no issues whatsoever.

Here are my specs:

Intel core i5 2500K
Gigabyte P67X-UD3-B3
8GB RAM
NVIDIA GeForce GTX 560Ti
Seatgate 1TB Hard Drive, 7200rpm

Any help would be greatly appreciated. I'm running out of ideas!!

I'll try another card, but I would have to put it under frequent use to be able to tell if that was the culprit. The freezing is so irregular that I have no idea of when it will happen next!!