I have a gamma issue

i have win xp and a geforce 2 when i start my computer it loads fone and all but when i play vertain games (hl) it goes normal till i quit the game then the gamma drops if i try to reset the gamme and go into game it does nothing its dark as hell have tryed to adjust all sliders and do everything i have found on the forum nothing works i have reinstalled xp and every thing my brightness s maxed on my moniter its quit frustrating when you want to play cs and yer moniters to dark so you have to reset yer com :stuck_out_tongue:
welp got to go reset now cause i want to play plz someone help me