oh, this is an older system. I didn't have much issue overclocking on LGA775 chip. It will be fine, just use Prime95 and watch the temps. If you start to hit 70-75, that's a little too hot. Chances are in games, you will never hit that temp.
If the multiplier is unlocked, I would leave the FSB alone and just increase the multiplier, run a heat test, than a benchmark and verify you are actually getting better performance. A bad overclock can degrade performance.
If it starts giving errors in prime95, or benchmarks crashing, that's when you need to increase the voltage.
The CPU cooler helps, but there are other areas that heat up, like the motherboard and the RAM. Your tower makes a big difference if it has good air flow, as does the fans you are using.
Research, experiment and tweak. Just be prepared that you are willing to lose all of your hardware if something goes bad.