please help me

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
Asrock K7VT4A Pro
Athlon xp 2400+
1gb ram
ac97
maxtor 80 gb
western digital 80gb
ati 9700 pro
xp professional sp2
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
Asrock K7VT4A Pro
Athlon xp 2400+
1gb ram
ac97
maxtor 80 gb
western digital 80gb
ati 9700 pro
xp professional sp2