security and inheritance

we are on a w2k server..my problem is when i want to apply security settings for a particular folder that may have 25 sub folders and i select the user who i want to have access to and tell it to allow it to propagate to the subfolders it will automatically add the users group and the engineering group and will not let me remove them with out taking off the inheritance…then i would have to go to every subfolder and do it manuall to just the user i want to have access to…why is this adding those 2 gropus automatically when i tell it to propagate to the sub folders? any suggestions would be great..
sr