I have Windows 7 64 bit, Realtek onboard sound.
I have USB speakers and today bought a USB headset. I can't seem to get them to both to work at the same time when plugged in. I usually like to keep the headphones around my neck while using the mic, but listen to my nice Bose speakers. When it gets to be late at night, just put the headphones on and turn off the speakers. Either way, the mic needs to work at both times.
They are both plugged into USB slots in the back of the computer.
When you plug the headset in, it negates the speakers.