Network migration

Thank you in advance for assisting me with my question.

We currently have an old NT Domain running on 100VG network. We need to eliminate 100VG so that this network can be inline with the rest of our Fast Ethernet. The NT domain needs to be replaced with AD 2003 (which is not a problem). My main concern is how do I get rid of 100VG (100vg supported switches and hubs included) while not loosing NT connectivity?