Cannot open Terminal on mac ("Not allowed to use" error message) I cannot open Terminal at all because of this error message. (Probably the rudest error message I have ever seen on a computer.) This mac was originally a school computer and the permission to use Terminal was not given to me in the first place, so I have no clue about the method the "IT guys" used to keep me from using it, and therefore I do not know how to recover from it either. I have an admin account, though the account I usually use is standard, (I tried logging into other existent admin accounts presumably set up by the IT guys, but even in those accounts it was impossible to run Terminal), and I have already tried running permissions repair but it had no effect on the issue.

(p.s. I am not a very advanced user of mac, so descriptions fit for a newbie would be very much appreciated. Have seen a similar question on this website but it did not really help.)
Your best bet would be to do a clean install, presuming you have copies / licenses for any software you use on there. Backup any files you want to keep, and follow one of the many guides out there. For instance:

http://mashable.com/2015/10/01/clean-install-os-x-el-capitan/

This could well take less time than figuring out what the IT guys did, and make your Mac faster in the long run.