There is no such setting in XP. Windows 7 has rewritten audio driver stack and it has a lot more control over the output. XP has rudimentary and archaic kmixer in the audio stack which does not allow the output bitrate. AFAIK kxmier will always resample the audio on the output, unless ASIO driver is used. For audio server it's highly recommended to use Windows 7. Also it's highly discouraged to use iTunes on Windows, as it'll add additional Quicktime layer to the audio stack and will make things more complicated. If you use Mac iTunes will work great. On Windows use j River MC.
