[Solved] Over Clocking a XFX 4850

I wanted to get the best possible performance out of my 4850. When I runt he auto tune the card eventually crashs. I'm new to over clocking gpu, been over clocking cpu for a while. Do i just want to increase the 2 levers and see if a game makes it crash. If it does back off? Is there an easier way to do this? I'm not sure why is crashing when I increase to far. It has not gotten above 45C. Another post recommend 690 and 1180. I tried that and it crashed as soon as I started gta4. Is there any utility that i can test clocks with. In cpu Ocing, i run a program liek toast to see if it will make it crash. Is there something similar o stress gpu?
Thanks

thanks for the info, unfortunately gurmark only is compatible with vista 32 bit, not 64 like I use. Also hawk is a game i would need to buy. any free recommendations that work with vista 64 bit?

Ok, thanks....dloaded, works great, what kind of temps are to high? Without maxing out fan i'm getting 60 degrees. Would it be bad to run toast at the same time? I was thinking of running toast on the 3 other cores because in gaming the cpu would heat the ambient air. CPU is not OC'd right now and my board prevents me from doing so (shitty intell board). The GFX is way more of a bottle neck anyway. I'm guesing running toast ont he 1st core ( the one being used for fur) would crash fur and thus crash the comp?
Thanks,
Cody

In my experience OCing ATI cards, an unstable overclock won't prevent you from loading windows, as the the 2d environment runs your card at a lower GPU preset. I have never had a problem loading windows after a GPU crash/lockup, and have always been able to go back into CCC to lower my settings.