If it was software you use System Restore (I'm guessing the OS is WIndows.)

If you delay too long, then that's not an option and you treat your PC like it was new, install drivers and configure. If that fails, it's a hardware issue and you pop in a sound card or use the warranty.

In my PC Medic bag I carry one of those under 10 buck USB Audio cards because of situations like this and how much time and money it can take to fix it.