Help a newbie w/ a Dual Core E5800

I am kind of a newbie when it comes to overclocking, and this would be my first one ever.
I own an eMachines (EL1850), which is a basic, bargain computer, but still, I wanted to get the most power possible from it.

The processor is an Intel (R) Dual Core E5800 @ 3.20 GHz
I also wanted to overclock teh GPU, but first I wanted to cover this.

The cooling is just fine, and in fact it's ready for some action