This post was in response to a now banned user who was posting questions copied from other users
Leave the Audacity Project Rate at 48000 Hz, but in Windows Sound,
you also have to set Windows Default Format for the mixer (both playback and recording) to 48000 Hz, with the Exclusive Mode boxes unchecked. Then choose MM£ host in Audacity’s Device Toolbar.
Alternatively, and probably better, enable the Exclusive Mode boxes, which means Default Format is ignored, but choose Windows DirectSound or WASAPI host in Device Toolbar. Oversimplified, those two hosts will recognise Exclusive Mode and should let Audacity request whatever sample rate is set in Project Rate directly from the device without Windows trying to use some different rate.
See http://wiki.audacityteam.org/wiki/Windows_7_OS#sample_rates for more explanation.