Is the root directory of the windows/system drive a protected area in
Vista or Win7?

I have an early recollection of that being the case, or at least of
having trouble updating files there, but I can't find it online.

All I can find on this is "In short, UAC monitors a list of
“protected” folders and registry locations (\Program Files, \Program
Files (x86), \Windows, and HKLM\Software); any time an application
attempts to write to one of those locations, it redirects the attempt
to the user’s “virtual store”." - See more at:
http://www.blackbaudknowhow.com/tech....ORUyWKRR.dpuf