When trouble shooting an issue it is best to isolate the problem and then re-step their setup, then back out any changes you made.
So first, make sure they are hooked up right, second try a different set (speakers are cheap 13 bucks at Wal-Mart if you don't have a back up pair).
The next thing is maybe the drivers and/or configuration (IRQ, I/O Addresses, etc...) for web-cam are disrupting your sound card.
Try uninstalling the web cam and rebooting. Try that and if they don't help let me know and we can go further.