My computer keeps on freezing up.

My computer keeps on freezing up. I'm 99.9% sure i dont have viruses as i scan daily an visit only a few websites. MY computer is 3+ years old, a toshiba satelite with a 1.66 ghz intel dual core processor an 1 gig of RAM. I think the issue is that it overheats as it gets EXTREMELY HOT. How do i fix this?
BTW, i havent been exactly taking the best care of it.
Please help