I installed WMPTagSupportExtender: the WMP library shows and plays (alas, some!!!) M4A files, FLAC and MPC files.
However, althought the added support file types shows, after you check them WMP does not maintain the file associations under Tools->Options->File Types. Anyone knows why???
And why not all my M4A files show in the library?
I run WINXP, WMP11, I have installed WMPTag 1.4, register the appropriate .dll, ran a and Tag Editor for mistakes in the file tags etc etc etc.
In a word, I seem to have done all things right. Havent I???