Speakers Stopped Working

My Dell INSPIRON E1405 (Vista operating system) speakers stopped working when I started using a Gigaware headset with boom mike, USB connection. Headset and mike will work with Skype; however, not with other applications such as Rosetta Stone.

When first used, sound was heard through the computer’s speakers and the headset at the same time. Prior to using the above headset I was using a Gigaware headset with boom mike and jacks without incident.

A diagnostics test on the computers speakers was successful. Please advise.

Thanks!