Counterstrike Problem?

Sometimes when playing counterstrike, and at bad times even multiple times per minute, my computer will freeze for 1 or 2 seconds, and when i look at the desktop, my computer usage is at 100 percent for some unexplained reason. My computer usage will sometimes be at 100 precent even when no programs are running. I have a fairly high power computer and it definitely exceedes the required specs for counterstrike, but i just cant seem to find out whats causing the problem