Computer freezing consantly some hlp wld be appreciated!!?

Computer was working fine yesterday but today its freezing up soon as i start a game like counterstrike..or over time when using older games. The computer freezes comppletly forcing me to restart my comp. Iv done virus and spyware scans and updated my drivers but still not hlpn resolve this problem. Any idea wut the cause cld be or some solutions? =]