Download Clockgen. It's a windows based OC'ing program.
Don't know why people forgot to mention that
Mind you, upping the FSB will be raising your memory and the AGP:PCI bus so you'll be quite limited to as how far you can actually push it but yeah, it sucks when people come in here and are like "Yeah I just got this brand new dell and I want to OC" and ya simply gotta say
"yeah....dell = POS"
Good for noobs and if you simply want to put in a new graphics card or perhaps RAM or something but getting beyond that it's not worth it.
I know you just got this old dell and whatnot, so the case isn't the same but yeah, they don't want you having extra options on a prebuilt