The current iMacs can extend the desktop to added screens. The confusion comes from the iMac G4 which did not allow for extending the desktop, only mirroring.
The MiniDVI to DVI adapter, may only have a DVI-D connector on it, so make sure the cable you use is DVI-D not DVI-I.
TEG
yeah i wasnt sure if i could extend the desktop cause i dont want mirrior. So all i need is a mini dvi- dvi cable and then go to setting or something to set it up?
I'm pretty sure you can, but I think you can only set up the screens to mirror. I could be wrong though.