Since it is SQL 2000, You will have to you will have to drop it out of Replication and then alter it and then add it back. Psuedo code for it that I use is like this.

1. exec sp_dropsubscription

2. sp_droparticle

3. Alter the table. Do what ever you want.

4. sp_addarticle

5. sp_refreshSubscriptions

6. exec sp_reinitsubscription

This si the method I know. Maybe someone has a better way.