But then, you're a die hard, and you still want to overclock the dell...
Sometimes, dell's are based on boards that appear in the retail channel as well. In even rarer cases, you could flash your bios with that of a retail board. Things you should know about this:
We don't know which dells are based on which boards, nor do we know which of those boards are based on known retail ones. Sometime google knows, so you should ask him.
Flashing will void your warranty. It's a risky business, especially when you are flashing with a bios that was not meant for your board. You risk losing your board, and everything connected to it. Don't do this if you aren't 100% sure that you know what you're doing.
Even if you manage to flash your board to a bios with minimal overclocking options, don't expect to get a big overclock. Dell doesn't buy the über high end parts, they buy the cheap mainstream parts... retail boards not meant to be overclocked.