px.dll related issues (file in use by other app, therefore installer can't overwrite it / ordinal not found errors etc)
http://forums.winamp.com/showthread.php?threadid=267149
http://forums.winamp.com/showthread.php?threadid=261083
http://forums.winamp.com/showthread.php?threadid=157326
http://forums.winamp.com/showthread.php?postid=1202637#post1202637
Note, there's hundreds more similar threads related to px.dll errors, but those are just 4 examples.
Proposed solution: Install px.dll in the Winamp root $INSTDIR instead of %system% dir.
Burning not working
http://forums.winamp.com/showthread.php?threadid=262516
http://forums.winamp.com/showthread.php?threadid=264137
http://forums.winamp.com/showthread.php?threadid=255809
Ripping not working: problem solved after advise to disable sonic and use aspi instead
http://forums.winamp.com/showthread.php?postid=1223065#post1223065
Sonic Engine crashing Winamp/kernel32 under Win98SE/ME
http://forums.winamp.com/showthread.php?threadid=239560
Sonic vs Windows Vista (32 & 64 bit) incompatibilty issues
http://forums.winamp.com/showthread.php?threadid=265735
!!!
http://forums.winamp.com/showthread.php?threadid=266497
http://forums.winamp.com/showthread.php?postid=2141676#post2141676
http://forums.winamp.com/showthread.php?threadid=265555
http://forums.winamp.com/showthread.php?threadid=265277
http://forums.winamp.com/showthread.php?threadid=265051
http://forums.winamp.com/showthread.php?threadid=261566
http://forums.winamp.com/showthread.php?threadid=261355
Misc issues
http://forums.winamp.com/showthread.php?threadid=263179
http://forums.winamp.com/showthread.php?threadid=261480
http://forums.winamp.com/showthread.php?threadid=262794