shut off monitor on an imac?

[stevf]

I have an imac dv and the monitor is slowly going out. This model is the first of the dv models and has a VGA out port that only mirrors the built-in monitor - you cant span on this model. Is it possible to shut off the monitor? Didnt see anything under system preferences. I have a spare lcd I can use, but i cant get the built-in monitor off. I use this as my e-mail machine, but can start using an xp or linux box if need be.