power user 
noun Computing
A knowledgeable and sophisticated user of computers.I would imagine that most systems not set up by a professional admin or a power user are running from the admin account by default, because most users are unaware of the security benefits of isolating, or sandboxing, users....
- Even within broad categories, be it a power user or a novice, per user approach differs.
- Whereas previously it was limited to specialists and business analysts, it has extended its focus to include power users and business users.