Installing exchange on sbs 2003.

Whoever installed SBS 2003 didn’t install exchange. I have the media on a single dvd. I tried to run the setup again and got an error message that it’s not the right version. Figured because it was SP2 on the server and the DVD is without the service pack. Uninstalled SP2, rebooted the server and started the setup again from DVD. I was prompted “NEW” or “Upgrade”. I chose upgrade and from there no questions asked. After couple of reboots, I’m in the same place as before. Exchange is not there. How do I install Exchange now?