HELP 9700 pro

Hello everybody.I have a problem, recently i won a 9700 pro but there is a problem.
the computer reebots fine gets into windows and everything works, even fs9 runs ok, but everytime i start games like Medal of Honor for eg. lines and forms apeear and wen i get out of the game. windows has vertical colored lines colored squares and the icons look like they only have 24 colors.Wen i reboot it some times it gets ok other times it doesnt i need to reebot until it gets ok.i have the 5.3 ati drivers on,win xp pro sp2 dx9c.
Help me
the computer reebots fine gets into windows and everything works, even fs9 runs ok, but everytime i start games like Medal of Honor for eg. lines and forms apeear and wen i get out of the game. windows has vertical colored lines colored squares and the icons look like they only have 24 colors.Wen i reboot it some times it gets ok other times it doesnt i need to reebot until it gets ok.i have the 5.3 ati drivers on,win xp pro sp2 dx9c.
Help me