I've 'sort of' answered my own earlier question.
 
On the portaudio web site I found the following:

Some advantages of using DirectSound are that DirectSound may have lower latency than WMME, and supports effects processing plugins. But one disadvantage is that DirectSound is not installed on all PCs, and is not well supported under Windows NT. So WMME is the best choice for most projects.

 
DirectSound - If you want to use the DirectSound implementation of PortAudio then you must have a recent copy of the free DirectX SDK for Developers from Microsoft installed on your computer.
 
 
_____________
According to that documentation (more at http://www.portaudio.com/docs/pa_tut_pc.html) Port Audio will work with both WDM and MME; however, the choice is really determined by my computer's configuration and whether or not I have DirectX installed.
 
_____________
 
Has anybody had any success with PD using ASIO MME?
Has anybody had any success with PD using ASIO WDM?
Has anybody had any success with PD using ASIO?
 
Regards
Dave S