Computer unusually hot all the time now?

If you haven't cleaned it out for a year or two its going to be full of dust. Buy a can of compressed air and blow it out paying special attention to the fins on your heat sink - the ram, all your fans (especially on the cpu and graphics card), and your graphics card. Don't use a vacuum cleaner (though I never take my own advice) because they tend to generate static. Static and electronics don't mix too good.