grub error 15
I have managed to break my system and am cautious now that I don't do more damage. This is what I have and what I did with it:
I have Deb squeeze and win xp dual boot and a data drive. Each of these is on its own physical drive.
Grub allows me to choose which os to run at startup.
I wanted to upgrade my win xp to win 7 and to avoid any confusion and potential damage windows could do, I turned the machine off, disconnected the power lines from all drives except the win xp drive, then booted up. Xp loaded fine. I inserted the win 7 upgrade cd but quickly found it is not possible to upgrade from xp to win 7 (thanks!!!) and so abandoned the idea.
I removed the win 7 upgrade cd, shut down, reconnected the power to the other two drives, rebooted and now the system won't boot anything - bios detects the drives as before but grub flags up error 15 and halts.
I have obviously broken grub but don't know what to do to get it back. Any help greatly appreciated.