xenarc power hook up
How would I hook up the power supply so that the screen would come on when the pc is powered on?
You could power it from a 12V line on the PC PSU, or put in a relay to the car's electrical system which is switched by the PC PSU.
Or if you were really wanted to, you could hook up a circuit to sense the sync signals in the VGA connector, and switch the monitor that way.
I have an Xenarc and I'm running it from the PC PSU (12v - Yellow wire) with an in-line 700ma fuse.
This way there is only power to the monitor when my PC is on.
Alos I'm luck enough to have one of the new Xenarcs which automatically powers up when a VGA signal is recieved and and automatically sizes the screen etc.