Second monitor issues

Hello,

My old Acer travelmate laptop 4050 has lost it's resolution on the screen, and is now really faint and you can hardly see anything. If you click the little button which picks up the screen closing you can get the screen flashing up normal brightness. Fully aware it's knackered and something has gone.

So here's the problem. I had the bright idea of using a VGA cable to use my TV as a monitor. Bought one, it's works straight away on my newer HP pavilion. Nothing on the Acer. Can just about see the display settings and have managed to get it to see the TV as dualview and can drag things over, but it won't work as the main monitor. Any ideas? It runs of XP., and I can't see why it can work as a dual, but not as main.
I would love to get all the pictures,etc off or even use it as a back-up PC.