Desktop not showing after system loads

I messed up big time. I was messing around with my monitor settings and I think made a mistake by setting the monitor to the wrong type..ie crt instead of LCD.
My laptop boots up fine but after Windows xp loads, I have a totally blue screen with nothing on the desktop. My mouse shows on screen but no task bar or anything. ctrl, alt, delete doesn’t even bring up task manager or anything that I can see.
I’ve checked some of my amibios settings and currently the first boot device is IDE-0 followed by CDROM and then BBS-0.
Any help would be appreciated.