Hello Will, thank you once again for your reply.
Yes, the M3 functions as a mass storage device, and appears in My Computer. If you have a moment, please take a look at this screenshot:
Note the drive is visible in Windows Explorer as 'E:'
I have arranged the music in the format E:\!Artists!\[artist name]\[album name]\
Each album folder contains the named tracks (mostly tagged) and a playlist.m3u.
Upon running WinAMP, I open the ml_pmp_usb.dll plugin configuration, then use the 'Manual Detect' option to select E:\ then click 'Connect this drive'. After a few moments, the drive appears in the 'Portables' tree as 'USB Drive E:'.
Below this, there are many 'playlist.m3u' entries that I do not really need to see (they do not display anything in WinAMP, perhaps because I have renamed/removed ml_playlist.dll) and are largely unnecessary.
Clicking the 'USB Drive E:' entry, I can indeed view the music on the drive, however only .mp3 files appears to have been added (most of my music is self-ripped .ogg format). Moreover, the SmartView columns cannot be modified.
May I ask how the ml_pmp_usb.dll plugin ought to be configured in my case? Perhaps entering correct information into the three File name format/Playlist Directory/Supported Formats textfields will help?
Another point to note is that WinAMP causes a GPF whenever I close the player after configuring the ml_pmp_usb.dll plugin, preventing any settings from being saved, thus requiring the process to be repeated each time.
Thanks again for your hard work chaps - I shall look forward to reading your response, and perhaps testing a new plugin.
EDIT: I note that performing the above process leaves a pmp_usb.ini file on the E:\ drive. Opening WinAMP once again and configuring the USB plugin, strangely only the playlist.m3u files are added. Closing WinAMP (okaying the gpf), deleting the pmp_usb.ini from E:\ and configuring the plugin once again, I find that the music is once again added correctly, albeit only .mp3 files.