Drooling over your OC's, I'm thinking of doing OC na din. First time. How far a C2D 2.0GHz can go (safe level)?
depends on your cooling and specific processor, each processor has it's own max oc levels (mileage)
i'd suggest get some temp monitors and benchmark softwares first, and see if your current settings is ok for OC (room for temp increase)
and then isolate each maximum frequencies of: FSB, RAM and Processor
when you up the fsb, ram and processor will go up as well, so you just have to lower the multipliers....
to up the ram, increase the fsb:ram multiplier, and lower the processor multiplier
and then for the processor, up the processor multiplier, and lower the ram multiplier.....
from that data, you could mix and match the best oc you could have.

be sure to increase the frequency in small increments only..

what's your motherboard?