My sound stopped working, suggestions?

[ChillPill365]

OK, so here's the dilemma. For the last few days, my sound has worked but my microphone hasn't (I have a Logitech headset with a microphone attached). Today I decided to look into the issue and to my surprise I managed to make the microphone work. This was all good until about 5 minutes later when my sound completely dropped out.

I checked to make sure nothing was muted, and I went into the audio devices and checked everything to make sure it was working properly, but when I right clicked on volume control and brought up the playback devices I saw that it said that the ATI HDMI Output was not plugged in. Everything else on there said that it was working.

Any suggestions?

EDIT: Never mind, I made my default device my speakers and now have sound again (although the HDMI Output not being recognized still bothers me).