Logitech Media Server (“LMS”). Free from http://downloads.slimdevices.com/nightly/index.php?ver=7.9. Note that this is the “community-supported” version, not the official Logitech version: it has some useful enhancements such as “additional browse modes”. Note also that Logitech stopped selling the SB Touch players (shame because they are excellent). Alternative players are available, e.g. Squeezecast or iPeng app on the iPod Touch, iPhone or iPad, or Squeezeplayer for Android. You can also use a Raspberry Pi as a cheap player (and indeed server). Max2play do several fully featured Raspberry Pi based systems. If you only want to play music on a PC then LMS is unnecessary. If you want the fancy “Custom Clock” screens on the SB Touch (or Squeezeplay on a PC) then you will need that plugin too.