Troubleshoot no audio out with an X-lite Softphone

Make sure your speakers or headphones are plugged into the appropriate port on your computer
Ensure that your master volume is not muted, or set to minimal volume.
Can you hear audio from other programs that play sound?
If you install a new USB sound device, it may become the Windows default sound device. Run the tuning wizard in this case.
Run the eyeBeam Tuning Wizard and ensure you select the appropriate sound device.
Is the other party actually transmitting sound? Ensure they have not muted their microphone.
Ask your VSP if they have an "Echo" test number, to test your audio.
Try installing the latest driver for your audio device. This should be available from your computer manufacturer.