Audiosonic KM 1903?

I want to use the TV as a pc monitor but when I start the pc the screen is blank. If I start the pc with the old monitor on it works, I can then disconnect the old monitor and connect the TV and it will work. When I turn off the pc and restart it the TV wont work again, so I have to start up with the old monitor and swap the leads every time. Anyone solved this problem.