Second guessing myself a bit on this one...here's the setup (not too complicated):
One Domain controller in 1 forest, 1 domain..running 2000 w/ sp4 and holds all roles. also running exchange 2000.
The basic goal is to upgrade the domain/forest to 2003 on new hardware and exchange 2003 on same new hardware.
1. Install 2003 server on new server, update
2. Join 2000 domain
3 run adprep/forestprep using 2003 cd on 2000 DC
4. Run adprep/domainprep using 2003 cd on 2000 dc
5. DCPROMO 2003 server
6. Transfer fsmo roles to 2003
****because of schedule I would leave it there for about a week***
**Exchange Migration** where it really gets fuzzy.
1. Run adprep/forestprep from 2003 cd on the 2000 server
2. run adprep/domainprep from 2003 cd on the 2000 server
3. Run setup/forestprep from exchange 2003 cd on server that holds schema (but now this role has moved)???
4. Run setup/domainprep from exchange 2003 cd on the server that holds PDC emulator (I don't think that matters)..but again, this role was transfered to 2003 server..??
5. run exchange cd and choose Deploy the First Exchange 2003 Server
6. Go through setup check list
7. After installation, update to sp2
8. **I believe I would create a new mailbox on the 2003 server and test mailflow.
9. Use move mailbox wizard to move to 2003.
***let ride for a while***Like a week
10. Uninstall exchange 2000 from the 2000 server.
11. DCpromo the 2000 server.