Game Sluggishness

Hello,

I currently have a big problem on my computer. When i first got my computer a couple weeks ago it was fine for all games and now there is offline game lag. Its too bad to play an games such as Battlefield Bad Company 2 or even Fallout 3. It wasn't there for a while and then suddenly happened I really need a solution thanks.

System Specs:
Alienware m15x
MS Windows 7 Home Premium 64-bit
Intel Core i7 CPU Q 720 1.60GHz
NVIDIA GeForce GTX 260M

P.S. Is Restoring my computer the best because I am currently making a back and a system image