I prefer 'Riva Tuner' ( www.guru3d.com ) over 'GFTU' & 'Powerstrip'. I use Riva to oc the driver (28.32 is VERY stable) & not the card. OC'ing the driver will oc the card too, but oc'ing the card doesn't oc the driver.
Use 'Detonator Destroyer' (@guru) between driver changes. & go slow on the oc'ing. If the system does 'lock', un-plug the comp for 15-20 sec & then re-boot. Riva will go back to 'safe' settings.
I've been using RT for months..very good proggy.
FYI....Detonator destroyer does not work with Win XP if ur using it, at least the last time I checked.