cannot access win2k(fat32)

in win2k(fat32)(complete succesful new setup)my client changed something(i will tell you exactly little later this day) in the network-systemadministrator-windows. to be precise: he deleted something and added new codes. now, despite knowing what he did, the system is blocked. how can he unlock it? i do not have the p4-machine in front of me. its far away.