UAC or User Access Control, in short, this is a layer of security prevent execution unless your account is permitted. This is how it looks on daily basis:

While doing penetration testing today, I ran into this UAC while trying to execute mimikatz to find credentials. This is my method so far to bypass this, so I started as sadams, which later on elaborated to mcharles using runas /savecred /user:SRV01\mcharles cmd. Due to this elaboration, I don’t know mcharles password, therefore could not fill in the UAC prompt.

Luckily, mcharles is also an admin due to the UAC suggestion. From the command prompt, start msconfig and launch Command Prompt from there.