Number One for XP is un-mapping the USBTD from XP and the dreaded Kmixer.
Go Control Panel => Sound and Audio Device => Select Hardware Tab => Select USB Audio
Device => Click Properties Button => Select Properties Tab => Select the audio device =>
select "Use audio features of this device" and "Do not map through this device".
Foobar is a fine playback manager, but you need to select the output device “USB Audio
Dac/Device” and work through the myriad of choices. When in doubt, just reset to default
and go from there.