Depends more on your motherboard and your cooling setup than anything. My suggestion would be don't bother. If you're going to overclock, do the research and start from scratch on a non-essential computer.
A P2 at 750 mhz? I've never heard man....Anyways...P2 450 runs on 440BX chipset(argh, I hate BX) which was the only way back then to raise fsb to 100mhz(I might be a little wrong on the history tho, sorry if I am). So, 450 mhz with 100 fsb and 4.5x multiplier. I've heard of OCing the fsb to 133mhz, ~600mhz(598.5)...or you cud try raising multiplier to 5x but this will not increase performance nearly as much as OCing FSB....anyways, u need a lotta lotta cooling for this...and I suggest keeping your case open.