Okay stupid stupid me! I was messing around with my laptop, and decided to delete my Linux partition as I hadn't used it for a LONG time. So, using Acronis Disk Director Server, I happily deleted the partitions and subsequently extended the secondary partition on my drive (to give myself some more room). Without second thoughts, I clicked the "Apply" button, and voila! the drive had been modified. Perfect. Now just reboot to make sure everything is still OK. "Hmm", I thought, as my screen went blank. "I wonder if I should have done something about the old bootloader before I rebooted". It was too late. GRUB happily said "Error 22" which probably means "Hey, dufus! I can't find my config file on that partition you deleted! Now what do you expect me to do?!"
I guess I'll just have to get hold of an XP CD so I can run an fdisk /mbr on my harddrive.