Nobody can really tell you what the OC limits are of your card. Thats part of overclocking, you just have to try and see what gains you can get. Even if you get your card to boot and run windows, only after running 3d apps for an extended period of time might you start to see artifacts. If you want to make your card faster, get ATI tool and play around with it!
"Who is General Failure, and why is he reading my drive?"
P4 3.0 HT, Intel D865GBF, 512MB Crucial PC3200 DDR, WD 36GB Raptor 10,000RPM, BBA Radeon 9600PRO, SB Audigy, Hauppage WinTV