In limewire go to Tools>Options>Player> untick the box that says "Use Limewire Media Player" then click "apply". If WMP is your default player all songs will launch in WMP. Here's another thread to check out:
Using windows media player
Also you can set WMP to auto add songs. In WMP go to File>Add to Library>(then choose a method). The default location for your limewire shared folder is C:\Documents and Settings\"your account name"\Shared.