License Manager

Hi,
I’m running a windows nt4.0 network.
Every once in awhile, I noticed that users I
deleted ,from the license Manager(that have left the company) have reappereared w/a license and I would delete them again. And sometime later they would reappear. Should I be using the revoke instead of the delete to permenatly keep them from reappering. Any help would be appreciated.Thanks in advance