nVidia Driver issues

Hey guys, been a while, right i got a problem with the drivers for my Sparkle 6600GT (AGP) as all of a sudden it's gone dodgy colours, then now, when i try to reinstall the drivers (NGO modified versions and official nvidia release) the screen cuts into power saving mode i.e no signal, anyone got any ideas?
Cheers
Benji
Cheers
Benji