GUIDE: 
The besa_upgrader_4.1.7.exe is an upgrade-only package.  It can be modified into a full install though:

1. Edit Setup.ini:
Under [StartUp] modify the following line:

CmdLine=REINSTALLMODE=vemus PF_RIM=1

to read:

CmdLine=PF_RIM=1


2. Use orca to edit "BlackBerry Enterprise Server.msi":
In the Property table, set UPGRADER=0
In the InstallExecuteSequence table, drop the row with the Action CA_CPPDLL_Upgrader_TerminateIfNotUpgrade


Now the install should run fine.