Sometimes...
Sometimes Window forgets to post icons in device manager, uninstall the sound card and reinstal/update the drivers then if it is still not working uninstall the rom and update the drivers. and don't forget to reboot the system after each operation. You may have cooked your sound card even though you can do it 1000s of times and nothing will happen your computer should be OFF when you put headphones or speakers into a system. You can fry a pooter if it is on, so you maybe looking at a new sound card bro sory to burst your balloon but that is the hard facts of computer life... USB & Firewire are about the only things you can plug in to a system hot and even then i would be very carefull as under some conditions you would fry the system, eg. it is -32 c out side 0-10% humidity your system and /or not a roller cart sit on carpet you come down to your computer Christmas day with a new Firwire External Harddrive, your system in on and as you plug it in you get a static shock you hear a pop sound and your system powers down... not a good thing... but I have seen this, buy the way that person only had to replace the PSU but it could have killed alot more and I am surprised it didn't.
Moral of the story shot down before you plug something in.