psexec told Couldn't install PSEXESVC service

Question

An account at Win7 is Administrator, the other is user1 as a normal user.
Administrator logon in session 1, I ran cmd as Administrator. I typed

psexec64 -i -u user1 -p 1 notepad.exe

But it told that

Couldn't install PSEXESVC service:
Access Denied

What's wrong with that?

Answer 1

Short answer: You need to run from an elevated/admin command prompt.

Details: psexec installs a service (PSEXESVC) every time you run it. The service is removed when psexec exits. To install a service you need to be elevated.