OK, I'm back up and running.

I managed to eject the disk and boot from my OS-X Tiger disk, and re-installed selecting to keep all user settings, and the desktop came back up after a reboot.

The only wierd thing is that the time and date have reset to 1994, I wonder if that has anything to do with it? I am doing a software update now so I guess I will soon find out if it was something to do with an update

Overall I am not very happy with OS-X at the moment, it leaves you high and dry without any idea what to do. I guess this is to make you take it down to your local Apple centre and pay them to put it right.

Thanks for all the tips, they were very helpful

Cheers

Cris.