It worked and now it isnt..!?

hmmm..

When did it stop working?

Was it after installing a program?
Was it after installing some other hardware?
Or did it work ok last night and not this morning?

but no longer does, and removing the sound device from her hardware device manager does not seem possible as there is none to remove.
And there are no "Unrecognised Devices" in the device manager? (these are devices with a big yellow Question mark, there are no devices with a big red X on their icon?

Has your friend tried or attempted to use System restore?

I wont repeat the questions of what the system is or type of MoBo.. these can be important..

/Edit: No one has been in the box and moved any little jumper pins by any chance have they?