windows sbs transition pack

A few years ago, I ran Windows 2003 Transition pack on a server and seemed to transition OK. Then I upgraded the server to 2003 SP1 and Exchange Enterprise 2003 SP2. I have recently become aware that the Windows PID displayed in the My Computer properties is for SBS not the standard Windows 2003 PID. The server once went into an activation loop running a Windows Update. Now I know why. Had to have Microsoft supply a special activation number. I would like to uninstall Backup Exec, delete the registry key mentioned in http://support.microsoft.com/kb/914990, and re-run the Transition Pack. I am concerned that I am now on Exchange Enterprise version with multiple mailstores. A associate has re-ran the Transition pack on Exchange Enterprise successfully, but that server did not have multiple mailstores. He did not have to reinstall Exchange Enterprise either.  How will the mailstores on my Exchange server be affected? Any advise or experiences would be helpful.