What happened to my computer?

So last night, I was playing the sims 2, but all of a sudden, while the game was loading, my computer froze with a continious high pitched noise.
The next day in the morning, when I switched on my computer, the PC wouldn't turn into PC mode, if you get the geist of what I am saying. I had to open my computer case to investigate further...
I noticed that all my components were working perfectly well (at least all the ones that remain obvious whether they work or not) but the component fans were stuck in a permanent-boot speed, i.e. very loud. My dvd drive sounded the "booting sound" twice for some reason. I used different RAM sticks and installed then in the 4 different DIMM slots, only to no avail. This omputer has been running fine for 2 years, why did it break down all of a sudden?
I suspect that my motherboard could be the culprit (faulty/failing DIMM slots) or it could be an overloaded Power supply. Please tell me what part of my computer is faulty? Thanks!

Here are my system specs for reference :

-Q6600 Intel CPU 2.4ghz
-650i SLI motherboard gigabyte
-X-fi titanium sound card
-7900gt GFX card
-1x 2GB kingston ram
-Dvd drive
-600W stealthxtreme PSU
-floppy drive
-network card
- 200GB seagate hard drive

I agree with with above post... may be a stupid question but did u reset cmos?

Unplug all the components that you dont need, extra fans, DVD drive, HDD, just leave the CPU, memory and Graphics card connected. See if the squeeling still happens. Try and locate where the squeeling is coming from. Also If possible pop the graphic card from your dads PC into yours.

Only two things left then.
Cpu has died.
Or the mother board.