Depends on the chip itself, what options your motherboard has, and what RAM you got. If you've got a 133MHz front side bus P3, you're probably not going to get as far as if you had a 100MHz FSB P3. Also, AOpen hasn't been a company that comes to mind regarding overclocking, and since I don't know the exact board you've got, I can't say how much you'll be able to take the CPU. I will say that if you don't have an adjustable CPU voltage, you won't get very far. Another factor that can put a cap on how much you can OC is what core you have. If you have the older Coppermine core, you're about at it's limit. If you've got the newer Tualtin core, you might get a decent OC out of it, pending other factors.
Like I said, it really depends on each individual CPU and what RAM you have. If you've got good RAM and make it to the 150MHz speed, you'll be running around 1.12GHz. That's if. Even if someone else hits so fast of speed does in no way, shape, or form mean that you will. Up the speed a few MHz, and see how it goes doing every day apps. Once you start noticing instability and/or odd behavior (programs closing all of a sudden, lockups, etc), either up the voltage a tad or back the speed down. Next try a little program called Prime 95. If it runs for 24 hours without an error, your CPU is stable at that speed.