Audio distortion with random CPU spikes

Hi All. I've searched the web trying to find an answer to my computer problem. There are other posts in this forum that have asked a similar question but I still haven't found the answer that works.

I have a new Win8 HP computer (2 weeks old.)

It has a Next Gen AMD Quad Core A-10-5700 Accelerated Processor
8 GB DDR memory
1 TB hard drive

I only have a few programs installed - iTunes, WinAmp, Camtasia, VLC Player, Google Chrome, MS Office, Paint.NET, Firefox and Carbonite. I had Panda Antivirus installed but just removed it thinking it might be using too much resources. So for an antivirus, all I'm using now is Windows Defender which is included with Win8.

So the problem I have is that quite often I'll get audio distortion and a lag on the screen while using the mouse. Sometimes, I may just be listening to music on iTunes or on Pandora while not doing anything else on the computer and still get the distortion.

Any ideas on what might be causing the problem?

Thank you so much.
Nat