I have a huge problem!

I know this is not related with top eleven but it has made my life miserable! I have a quad processor and for some reason only one of them works, this makes everything to function as there is only one processor, the tabs on chrome load one after another, I can't play games, I can't have many programs that function on the background open at the same time and in general everything goes as fast as a snail. I try to hang on and work like that cause I don't have money to buy a new PC even though I made a really good one for only 700euro... So if anyone here has any clue that can help me fix that I will owe him big time. If he is on server 6 I will give him a super gift! XD