Yes, as long as you keep at least one existing DC up while you upgrade the rest. If you have two DCs, run dcpromo on run to remove it from the domain. Then you wipe that box and install 2003.
Run adprep /forestprep and adprep /domainprep on the remaining 2000 DC. Then run dcpromo on the new 2003 server to promote it to a DC.
Now run dcpromo on the 2000 DC to remove it from the domain. Wipe it and load it with 2003, and dcpromo it to a DC.