Sound on a computer? by MH

Some years ago I rebooted my first computer and the reboot took the sound away and not knowing what to do, I eventually had to buy a sound card, etc. The other day I rebooted a computer for the kids to use to play games and again, the computer is like it just came out of the box, only it has NO SOUND and says No Sound card found! I spent probably 2 hours attempting to figure out how to restore the sound, from what I figure it needs what they refer to as a "driver" reinstalled? The computer came from the factory with sound and surely is capable of it again, but I am at a loss how to figure it out and it is worthless as a game playing computer with no sound.

Does anyone know how to solve theis problem after you have allowed the System Restore to reboot the computer to new condition? This has happened twice now to me, so it must be a common problem.

Thanks,
MH