Might be a sound card issue, but not with the sound card.
I have a USBPRE that I can connect to the computer and then record audio by connecting my source (CD, DVD, etc.) into it. However, if I boot the computer with that connected to it, the computer reads it as my audio card...consequently, no sound from the speakers.
I have to disconnect it, reboot, and the reconnect it if I want to use it. Make sure your audio preferences are correct by checking "Start" "Control Panel" "Sound Devices"
Hope that helps.