Just to update on this problem. I went away for the weekend and turned th PC off at the wall socket. When I came back it started first go and fired up the Monitor. Not sure what that means, over the next two days I turned it off and on a few times and it all worked fine. I got one blue screen of death during this indicating a fault somewhere, I restrted and it was fine.
Today when I went to turn it on the monitor wouldn't work again. So I turned it off at the wall for a couple of hours and turned it back on and the monitor started. Does anyone know what this means and whether it indicates a fault somewhere in particular? I had assumed it was was vid card but it seems to work ok when the monitor is on.
Thanks