Cannot transfert Schema Master Role

First, I had only one DC for my domain. DNS, WINS and the 5 FSMO roles were installed on this DC.

Then, I Installed an additional DC to this domain. I wanted to transfer the FSMO roles onto the 2nd DC, which I did successfully for the RID, PDC, Infrastructure and domain naming master roles.

When it came to transferring the schema master using the Active Directory Schema Snap-in of the MMC, it would not let me. The button “Change” was disabled. Anybody knows why? Anybody knows how can I go around that ?

Both DC are running Win2003, the second one has SP2 installed and does not have DNS and WINS. The first one has SP1.