Bart,
The following is pasted directly from the Help and Support Center, search on
"power users".
Hope this helps.
Power Users:
"Members of the Power Users group can create user accounts, but can modify
and delete only those accounts they create. They can create local groups and
remove users from local groups they have created. They can also remove users
from the Power Users, Users, and Guests groups."
"They cannot modify the Administrators or Backup Operators groups, nor can
they take ownership of files, back up or restore directories, load or unload
device drivers, or manage the security and auditing logs."
Users:
"Members of the Users group can perform most common tasks, such as running
applications, using local and network printers, and shutting down and
locking the workstation. Users can create local groups, but can modify only
the local groups that they created. Users cannot share directories or create
local printers."