Extended Desktop is not working in Windows

I used boot camp to install windows XP, I had a monitor plugged into my MBP at the time and it started up with the displays mirrored. When I installed the Mac windows drivers and restarted the monitor no longer worked. When I go to the Windows display preferences it shows the monitor as there and connected in extended desktop, however my monitor insists that it has no signal. Also - When XP is starting up the monitor mirrors what's on the MBP monitor - it goes blank only after windows is started up. I have tried getting drivers for the display, video card ect. Anyone have any ideas? - Thanks