I installed Audacity 2.0.5 and from that moment, no sound at all works on my computer: not even blip prompts. The sound card and all drivers are good. The speakers and headphones are all good. Any thoughts?
If you have just connected a USB microphone, turntable or cassette player, see: http://manual.audacityteam.org/o/man/faq_playback.html#usb .
If that does not help, please tell us what version of Windows you have. On Vista and later you can select the default playback device in Windows Sound .