After a bit of GOOGLE-ing this popped.
http://windows.microsoft.com/nl-nl/windows-vista/windows-update-error-800b0100"Files not correctly registered".
Try this:
1. Grab the latest Windows Repair (WR) version (v2.01)
2. Run (at least) the repairs #1, 2 (select drive on which your system is installed), 3, 6, 16, 25 & 26. (some people simply run all repairs)
Reboot. Is the problem solved ?
3. grab the file in the attachment, unzip it, switch off internet and run it with administrator rights.
Reboot. Is the problem solved ?
If step 3 helps to solve the problem then I know where WR needs to be improved (Shane ??)