Originally Posted by S0ULphIRE
Open up your case, check the fans/heatsinks aren't completely clogged with dust.
After that reset the BIOS and hope nothing's been fried. Though by the sound of it something might have died already.
Agreed. Sounds like you had a thermal event and over a period of time (all the freezing) you finally fried the part.
Since it is getting power you can bet it isn't the Power Supply, and since it isn't beeping it is more than likely the motherboard. If you have an onboard audio speaker your computer will give an error code beep when something isn't working (RAM, CPU, GRAPHICS, HD). If your computer doesn't have this speaker you can purchase for for really cheap and plug it onto the MB.
If you DO have a speaker onboard and it has beeped in the past when something was ary, then you've probably fried your MB.