I tried to switch monitors using the <Fn><F6> key combo and turn off the
machine. This process failed, and the laptops display reverted to
default (on). It sounds like you tried Ubuntu from CD rather than
install, so doubt your experiment with Linux caused any problems. It is
highly unlikely that Ubuntu caused any of this kind of problem anyhow.
I have installed Ubuntu on many Toshiba computers, my own computer
included, without a hitch. Make sure the CD is out of the drive and try
starting the machine again. This time look to make sure the Toshiba
splash screen displays, if not I would guess a hardware problem. You
might also try starting the machine with CD in as it would come up using
the CD if your boot order was set for CD first, this removes question
about any writing that was done to the hard drive.

Let us know what is happening with your machine.