SNAFU.
On saturday I had to load some security and update patches on some of our print servers that run Xp embedded.
The first one went ok but the second and third went completly tits up and started giving the BSOD after applying the last patch. I discovered that somehow I'd managed to delete most of the files from the patch, which was on a memory stick, after applying it to the first machine.
fortunately I was able to restore both servers from back up and only had to reload the extra applications but I was still here 'till nearly 4 o'clock tho'