HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList
This key contains keys named after the SIDs of users that have logged into this machine.
In these keys you can edit the path of the user profile, in the ProfileImagePath value.
You can also manually delete user profiles by removing their appropriate key (identified by the SID named keys, or the ProfileImagePath value inside each key, which has the current profile path) whilst also deleting their user profile folder, usually in C:\Users.
If you delete a users profile from C:\Users, without clearing their associated key in the ProfileList key from the registry, when they next log in they will be generated a ’temp’ profile, and Windows will display a notification to them to that effect. Typically with a path along the lines of C:\Users\TEMP, sometimes appended with the domain’s NetBIOS name/UPN Suffix: C:\Users\TEMP.NETBIOSNAME.