i have a gf4 ti4200 triplex millemium silver.. big heatsink and fan and everything.. now i know i should be able to o/c the card to 320/650.. i have riva tuner latest' version.. when i o/c i cant get the mem over 550 without getting artifacts..! the core wont run faster than 290 also (i will also get artifacts in that situation when i'll turn on a 3d game).. if i put a lil more mem or core i get my card to stop responding and shutting down.. can an expert give me good advice on how to o/c properly..? i dunno.. from the bios.. but riva tuner is pretty good.. only not for me..