Pre-game editor (which mean you need to start a new game everytime you modify a new game):
C

Program Files\Sports Interactive\Football Manager 2005\fm data editor.exe
and the user guide:
C

Program Files\Sports Interactive\Football Manager 2005\fm_data_editor_guidelines.pdf
There is as well Real time Editor
MCFM05:
MCFM05 v0.5.0
Legendary real-time editor with new updates and additions on a regular basis.
and there is FM Scout:
FM Scout 3.22
A utility which enables the user to see ability stats and values without the need to load up the game itself or the editor.