Try the following.

1) Change the settings of audio particularly if you have installed an external sound card - in that case disable the default sound card of your PC.
2) Try ASIO instead.

3) Close any other application using audio resources.
4) Run application as administrator.

There can be many other reasons, however, since I am unaware of your operating system and computer I have given the most generic solutions which should work in majority of the cases. I hope it helps.