Kerrie "did something" to her fiancée's lap-top resulting in the loss of all Windows System sounds, also all sound using Firefox, though iTunes & RealPlayer produced sound just fine.
On Start >> Settings >> Control Panel >> Sounds, the Play button for System sounds was greyed-out. The record & play buttons on Sound Recorder were also greyed-out.
After many hours of unsuccessful tinkering, the problem was eventually solved HERE.
K-Lite Codec Pack 7.1.0 STANDARD version also contains a very nice Media Player.