Per . . .winston:
Not possible...the update to update the 'updating engine' is less than
3/100 of a percent of 30 GB. Windows Updates larger than 1GB are
extremely rare. I can't recall a single one during the life of Win 7 o r
8x. The largest Win8 update was the 8.1 update and it was under 1GB.

30 gigs sounded crazy to me... but I could not come up with any other
explanation - even after running WinDirStat and stepping through all the
directories.

I'll keep an eye out... that same update is lurking somewhere, and when
it strikes my re-imaged system I'll do a quick "Before" check and then
note the "After" space.
--
Pete Cresswell