I posted a similar thread here:
http://yabb.jriver.com/interact/index.php?board=3;action=display;threadid=20903 but no one seemed interested
The plugin you need is called Highly Experimental (don't worry though, its quite well developed now
) and you can get it here:
http://www.neillcorlett.com/psf/The site states that "Highly Experimental is a plugin for Winamp that plays PSF and PSF2 files. It features a tag editor, configurable title format, options for song lengths and silence suppression, well... everything you'd expect from a Winamp plugin, pretty much."
Unfortunately though, functionality will be limited in MC to simply playing the file (no title name, tagging etc) as J River seems unwilling to implement better plugin support, so you won't be able to read info from the tags <end subtle hint>.
Alternatively, although I hate recommending another player, foobar2000 (
http://www.foobar2000.org/) is another (free) option if you are serious about these files. The latest 'special' version has native support for PSF files (as well as SPC, NSF & GYM) and can read the tags through plugins, something which MC lacks with most plugins.