Problem Solving Needed

Greetings. I am having issues with my computer. The problem is it gets super slow almost freezes then catches up rapidly. Loading web pages is slower, youtube is laggy. When I play world of warcraft it really shows as it won't load things until 30 second at arriving at a location. How ever I still see text and can send texts in game. How ever I can play Battlefield 3 with almost no problems.

I am a novice/intermediate skilled PC person. I built my computer on my own and have not had any issues until today 4 months after building it. I constantly update my drivers.

here are my specs.
Windows 7 home premium 64-bit
Ms-7673
intel(r) core(TM) i7-2600k CPU @ 3.40GHZ (8CPUs), ~3.4GHz
4096MB RAM
GEFORCE GTX11 550-i PNY
Directx 11

The only thing I can think of is it is overheating, but why would it do it now?

 

Run chkdsk yet?

http://support.microsoft.com/kb/315265