Why isn't my MAC desktop accepting my admin password?

[iMore Question]

MAC desktop doesn't accept my admin password

When I sign in to my computer and it asks for my password, it works to open it. If I try to change, delete or download anything while using my computer and the screen pops up and asks for an admin name and password it doesn't work.

 

[Bigeric23]

Re: MAC desktop doesn't accept my admin password

Is it your machine? Are you an admin on that box?