It sounds like you may be better with the unzipped version rather than a full install.
Not sure why the full install wants to set up outside the local drive so as you say maybe an IT dept. setup issue.
Corporate and Educational boxes can be very fiddly to set up. Also be aware that a "user" with admin rights is NOT THE SAME as a full administrator.
Attaching some clean up help in case you want to try the unzipped version.
CLEAN UP BEFORE INSTALLING ANOTHER COPY OF THE IDE OR ARDUINO CREATE.pdf (345 KB)