Steam games crash to desktop with no error message

[Above All Laws]

I will be playing a game. Any game on Steam that is multiplayer. I'll be playing... everything is fine.. then the server will change to a new map. Cool a new map! Loading.. loading... then all of a sudden, screen goes black for a second and my desktop appears. The program is no longer running. It is as if nothing happened. There is no sound, there is no error message. I'm really troubled by this.

THIS IS AFTER A FRESH WINDOWS XP REFORMAT AND INSTALL.

This only happens with steam games. No other games.