first of all you need to tell us more about your system....what mobo, cooling, video...etc...if it is a major branded computer (compaq, Dell) then you will not be able to oc or if its and Intel mobo.....
the best guides to ocing can be found on the front page of www.overclockers.com in the Begginer's Guides Section, they explain it much better than i can....be sure to ask more questions
Well I did buy it from Dell. It's a Dimension 4100. I got all this info from Sandra.
Processor speed: Intel PIII @797MHz
Packageing: PPGA Socket 370
Model Info: P6C (Coppermine) P III E(B) 500-1.13G 1.3-1.75V
Supported speeds: 800MHz or more
Supported voltage: 1.6V
Manufacturer: Intel Corp
Model: Intel Corp 82815/EM 815/EM (Solano) Host I/O Hub bridge
Front Side Bus: 133MHz
I have 384 MB of PC133 ram, primary HD 20G, secondary HD 40G GeForce 2 Ultra 64 video card.