On Friday I decided that I would finally remove my Windows XP partition, not realising that the files required to boot both Windows XP and Vista were stored on that partition.
Now I was left with a system that would not boot, and for some reason the repair option refused to work. I really didn't want to wipe the system, even though I can back up my files to my other hard disks, just because it takes so much time to get Windows back to normal. Skip to 22 hours later when I thought I would try putting the DVDRW drive onto a different controller - the machine was working in 10 minutes.
If only I had tried that when it first happened, I wouldn't have wasted a whole day :(