Hello,
Before starting any operation, backup of system state and exchange is must. you can follow these steps ( as a best way to migrate) to do an "in place" upgradation.
First of all exchage server 2003 requirments need to be fullfilled. your present windows 2003 server must have service pack 3 and exchange 2000 with service pack 3.
When we are doing "in place" upgrade from 2000 to 2003, you have to upgrade exchange 2000 to exchange 2003 first and then windows 2000 to windows 2003 becuse exchange 2003 does not run on windows 2000 server.
In upgradation process you can following these steps:
First of all verify NNTP, SMTP and IIS are enabled and working find.
Then remve the follwing services (these are not supported by exchange 2003)
Instant Messaging Server, Chat and Key Management Server, Lotus cc:mail connector and MS Mail connector
Then check the DC and network functionality with DCDIAG and NETDIAG tools with are available with support folder in windows 2000 server cd.
Then run the follwing commands
CDROM\setup\i386\setup.exe /forestprep
CDROM\setup\i386\setup.exe /domainprep
CDROM\setup\i386\setup.exe
After Exchange upgradation now you can upgrade windows 2000 server with windows 2003 server.
To upgrade windows 2003 you have to run the follwing command from windows 2003 server CD
CDROM\i386\adprep /forestprep
CDROM\i386\adprep /domainprep
CDROM\i386\winnt32.exe and start upgrade
By using all the above steps I have upgraded so many servers in different companies.
Best of luck
Balkar Singh