I'm no technical person, but I'll throw this in just in case: I have a Sony viao desktop and thought that I would use my DVI output to my plasma screen and the VGA to feed through a TV converter to our kitchen TV, but the DVI and VGA don't work simultaneously, which, in non-technical terms is just about where you are.

I should have added that, at the time, I took it to the Company who provided the support at my office who connected screens to both outputs and spent a long time playing about, but couldn't solve the problem.