I found Windows XP SP3 on another machine, burnt it to a CD with ImgBurn (using an old .img file to go with it), then booted and chose R, the Recovery Console, then after some hemming and hawing, I ran fixmbr, and then it rebooted into Windows fine. But I am just lucky that my parition table was not moved by Linux or at least not in a way that was not recoverable. I should really take my backups of the MBR to CD - would have been easier using HDHacker or some similar tool. At least I have Windows. Done for the night. I could also back the files up to a USB stick since I don't have a writeable CD/DVD on that machine, nor an Internet.