i havent overclocked before but after moddin' everything else (apart from a new processor heat sink and fan) i think its about time i started.

can anyone give me a few hints and tips (and if anyone has one handy a step-by-step guide)

My computer is a:
Intel Celeron 2.8GHz 400MHz
512MB RAM
with a NVIDIA FX5700 256MB graphics card

either of these look like a fairly decent overview on overclocking...

Overclocking - An Overview (http://www.pcmech.com/show/processors/132/)

How To OverClock (http://www.basichardware.com/how_to_overclock.html)