Recs.
Updated
MusicBee is a media player/library manager for Windows, written in Visual Basic .NET and freely distributed by the author. It organizes collections of all sizes, is highly customizable with third-party plugins and skins, and intelligently scrapes data from several trusted sources to update any empty tags or artwork in files you play.
SpecsUpdate
Pros
Pro Customizable look and feel
MusicBee can be skinned which can significantly change the appearance of a player.
To apply a skin, it must first be downloaded, moved to the appropriate folder, and after restarting MusicBee, it can be applied. A collection of skins can be found here. It's also possible to customize the layout by choosing which panels to display.
Pro Vast library capabilities - handles a massive collection of music with ease
Current file count exceeds 500,000+. Updates the library faster than other similar feature rich players whilst being fully capable of playback, id tag editing, even visualiser generation simultaneously, limited only by the power of your PC. If your experience is different you likely don't have a capable machine.
Pro Remarkably responsive interface with small to medium numbers of files
Your media library is stored in a flat file rather than a traditional database, limiting its ability to manage truly massive collections of audio files, but offering far reduced processing overhead for small to medium-large collections.