Hi all - totally bewildered - not a problem with Audacity, rather windows I believe - I can’t monitor sound when looking at and playing the audacity files. They play fine when I export them to MP3. I’ve checked mixer levels etc. What am I doing wrong?
What you are doing “wrong” is not answering the questions in the pink panel at the top of the page and not telling us more about what you are trying to do. 
If it is just a problem with playing audio in Audacity that has already been recorded or imported, look in Device Toolbar which is outlined in red here:
[windevtool][/windevtool]
and choose the correct device (by the speaker icon) that you are trying to play to. If the green playback cursor is moving and the green playback meters are bouncing and you still can’t hear sound, restart the computer.
If that doesn’t help or if you are trying to record while playing, please describe the problem in more detail.
Gale
Audacity can route and play sound independently of whatever Windows is doing. Use the Audacity Device Toolbar to set there playback audio is going.
http://manual.audacityteam.org/o/man/device_toolbar.html
You can also set this in Audacity Preferences.
Audacity > Edit > Preferences > Devices.
Koz