I have two (supposedly) identical servers running Windows 2003 server. When I put my Digi Acceleport card in one box the 16 ports show up correctly as ports 3 thru 18. When I put the same card with the same driver in my second machine, the ports show up as ports 19 thru 34.
The numbering of com ports is not a default, its a number based on whatever com ports are already in use on the server where the serial card is being installed. So, on the second machine I believe that ports less than 19 are already in use, or possibly still exist in the registry due to a previous install. If you’re able to free up com ports lower than 19 on the second server, you’ll be able to re-number the Digi com ports to use those unused/freed-up com ports.
Michaelt’s reply is correct. Here is a link to an article about how to remove these “phantom” ports in Windows Xp, but, the same steps can be used in Windows Server 2003: http://www.digi.com/support/kbaseresultdetl.jsp?id=274