Here is a link from someone else on this forum who pin-modded a e520.  Maybe you can get together with him/her to learn all about it.

 

http://www.dellcommunity.com/supportforums/board/message?board.id=game_overclock&thread.id=8699

 

User: Slop

You are not meant to be able to overclock that system.

 

The only way you can is to physically change the crystal oscillator which controlls the FSB (requires much knowledge and electrical skills - [EXPERT]).

 

Or you can "pin-mod" the CPU.

 

I don't know much about pin-modding, but stuff can be looked up and read.  Here is someone else's pin-modding experience:

http://entertainment.webshots.com/album/558927258zYEygr

 

Mombodog had a pin-modding link which was pretty good, but I can't find it.

Overclocking a Vostro 200 400 or an Inspiron 530 involve modding the CPU it self to increase the FSB from 800 to 1066 or 1066 to 1333.  You don't say what CPU you have but since it's at 2.33ghz chances are it's already running at 1333FSB so there's nothing you can do on the stock mother board.