The computer of my brothers girlfriend had problems. Tried to install the win xp harddrive of my parents (which contained some software I wanted to use) in her win me machine. It didn't work (probably fat32 vs ntfs). But when I reinstalled my parents harddrive into their computer, the disk wasn't detected anymore. After a lot of searching with recovery tools, it appears that the boot sector was changed. It was reported as a fat32 disk while the files where in ntfs format. I managed to get my parents data from their disk (with GetDataBack, a recovery tool), copied it to my laptop and reinstalled their operating system. One day lost because of this... But now we have again two healthy computers and one lesson learned (although I already knew this): don't ever, under any circumstance, use or try to repair Windows Millennium again!
Murphy's law kicked in a lot: in each machine, a cable became loose (ide and floppy), the date was incorrect which caused Windows Update to refuse to update and spyware on one of the machines which slowed the whole process down.