External Sound Card / Internal Speakers?

Greetings!

The headphone jack on my Sony Vaio notebook has a "loose contact" and it is no longer possible to listen with headphones. So I bought a USB sound card and plugged it in. That works fine when you are listening through the headphones but the card seems to hijack the whole sound system. It installs itself as THE sound card and the original card is disabled. If I boot up the machine with the USB card it automatically installs itself (logical enough). If I then want to just briefly listen to a file without searching for my headphones it is not possible. The internal speakers are not running through the USB sound card. If I go into the Control Center and change the sound card under "Audio" I can then listen through the internal speakers. But this is a real pain. I tried using Device Manager and the Audio in Control Center to see if I could re-route the internal speakers through the USB card but I couldn't even locate them let alone re-route them. If anyone out there knows how to do this I would appreciate the tip. Maybe it's just not possible. One or the other.

If I bought a PCMCIA Soundblaster card would I have the same problem?

Thanks,

Dave