Easiest answer is to turn Pause-sound off. That's more of a system setting though. Check your system sound settings for this possibility.

Stick a CD into your computer. Open iTunes & see if it can play the songs. Let us know what happens.

Are you using headphones or output from computer to speakers/stereo?

Did you consider using the Add/Remove ->Repair option for iTunes? An example almost deleted now for LimeWire is described in step 4 here: Fixes for Limewire (it no longer applies to LW so it doesn't have any relevance to LW, but only other programs.)