Go to this page:
Notice that every update has a code, like KBnnnnn ? Now search the c:\windows folder for a file containing KBnnnnn in the filename (try a bunch of them codes).
If it is a .msi file then you may have found the directory where vista stores all the updates as msi files.
.msi files are windows installer files and they can be copied and run by double clicking on them.
If you have too many files, try searching for msi files only.
This method is not guaranteed to work.
Sorry, I dont have vista anywhere near me, so I cant test it and give you detailed instructions, or understand what you're doing wrong.
Good luck