Mike
I've had success hacking the registry. You're welcome to try this, but beware that it comes with the usual caveats about backing up the registry first to avoid trashing your system.
The jist of it is you create a VBS file - these files hold commands that Windows can carry out - then run it to choose the midi mapper that you want.
To create the VBS file, you first create a text file by right-clicking your desktop and selecting New - Text Document. When you name the document make sure it finishes with '.vbs' and not the usual '.txt'.
Now open the new file in Notepad by right-clicking the file and selecting 'Edit'. Paste the following code into it:
//Code START
prompt = "0. GS Wavetable" & vbCrLf & "1. Roland RD300SX" & vbCrLf & "2. Roland SoundCanvas Out A" & vbCrLf & "3. Roland SoundCanvas Out B"
i = InputBox(prompt, "Map to a MIDI device")
Select Case i
Case 0
i = -1
Case 1, 2, 3
Case Else
i = 1
End Select
Set WshShell = WScript.CreateObject("WScript.Shell")
path = "HKCU\Software\Microsoft\ActiveMovie\devenum{4EFE2452-168A-11D1-BC76-00C04FB9453B}\Default MidiOut Device\MidiOutId"
WshShell.RegWrite path, i, "REG_DWORD"
// Code END
(note that the line start 'path = ' above may get wrapped in this forum because of the page layout - that particular line starts 'path =' and finishes with '\MidiOutId'.)
You'll see that I'm the owner of Roland equipment, hence the wording in the code. Save the VBS file then double-click the file to run it. If you choose 0 then you'll stay with the default Windows MIDI sounds. Windows then allocates 1, 2, 3 etc to any other
installed MIDI devices.
Best of luck