I guess we should thank Mr Mutschler for declaring it public domain and making the source available.
That enabled someone to make it a project on SourceForge
If you Browse All Files
there, the 3.4.23 file is the same as the V3.4b23 version available from the author's original www.mutschler.de/mp3ext/download.html
The mp3ext_3.4.24 file was the first one compiled for 32 and 64 bit, and
the mp3ext_3.4.25 file there (which is the one you get by clicking the green Download button on the 'project on SourceForge' page) has been tweaked for support of more players.
As usual, the modified source is available using the subversion client of your choice: sourceforge.net/p/mp3ext/svn/14/tree/
though I believe you have to 'join' the project for check-in permission.
Anyway... I've installed 3.4.25 on a couple Windows 7 x64 computers, and have not had any problems with it, so far.
I'll save my complaints about the slug MS calls Media Center for another thread.