Ok. It's not a big deal, I just want to change a players position of mine so I don't have to waste my draft picks on that position when I don't really need to..
If you want to change a player's primary and secondary position, it's simpyl a matter of changing their POSITION and POSITION2 values in players.dbf; 0 for centre, 1 for power forward, 2 for small forward, 3 for shooting guard and 4 for point guard.
However, that's something you can edit for your own players in Dynasty Mode through Edit Player so there's not really much point in doing to the trouble of editing them via the DBF.