Since the official winamp.com site now hosts a completely redesigned "New Winamp," you can usually find this legacy "Full" installer on reputable archival sites like: FileHippo The Internet Archive (Archive.org)
: While "Pro" originally meant paid features like high-speed CD ripping and native H.264 support, the "Pro" installer for 5.666 was eventually made available for free as the service was being wound down.
: Ability to sync your music library with the Winamp for Android app. Installation Note
Since the official winamp.com site now hosts a completely redesigned "New Winamp," you can usually find this legacy "Full" installer on reputable archival sites like: FileHippo The Internet Archive (Archive.org)
: While "Pro" originally meant paid features like high-speed CD ripping and native H.264 support, the "Pro" installer for 5.666 was eventually made available for free as the service was being wound down.
: Ability to sync your music library with the Winamp for Android app. Installation Note