Sound...of silence

Hi,

First up, I'm no tech guy....

My computer (Windows 7 Ultimate) recently went back to its makers for a service and installation of a new blu-ray player (the old one was no good).

Almost everything is perfect. I use the computer with my HannsG281D monitor as an HDTV. The TV is perfect with lush sound and pictures.

I have a two-way switch to alternate between TV/computer. When I change to computing mode - NO sound. I've done all the usual checks - audio jacks cable, Volume Mixer, Sound Manager, updated drivers etc., and everything is working properly in Device Manager - but NO sound!

I seem to remember in a previous time two computers ago that I had a similar problem which was blindingly easy to fix...unfortunately I'm older and the brain cells containing that memory have been destroyed by high living and general degradation...

Any kind, intelligent soul out there with any (simple, remember) solutions?

Solve this and the children of my village will sing thy name...loudly!