Argh! User deleted packages from their machine, now sound is broken

[Michael S. Peek]

Hello Ubuntu gurus,

Long story short, I have a power-user with root access on his own 
machine, who has decided to remove some "unnecessary" packages.  Now 
sound doesn't work on his machine.  Is there anyone who can tell me how 
to find a list of just the packages are related to system sound, so that 
I can check, reconfigure, and reinstall any missing packages?

Or, does anyone know an easier way to fix a problem like this?

Michael