How to Unlock a User in Microsoft Dynamics GP

This is useful in solving Dynamics GP error: "User is already logged-in" when you are trying to log into Dynamics version 7.5 and below.
For version 8 and above, a better way is to remove them in the User Activity window. Go to Setup - System - User Activity, then choose the user to delete.

SQL Command:

DELETE FROM ACTIVITY WHERE userid='username'