Sound not working on my PC

I've got Cambridge Sound works analog speakers (DT2200) 5.1 system from about 2001 still going strong (about the only thing about my PC that hasn't changed). The mini speakers and subwoofer are really great, I use 3 of them L,R,C and don't bother with rear speakers as it's quite a lot of wires.

Anyway, just now the sound stopped working. I've just spent an hour trying to workout why. I went through all the obvious stuff like 

• do the speakers have power
• are all the cables plugged in
• check the volume isn't muted
• check the volume settings aren't too low

Then I tried a few more esoteric solutions:

• Windows 7: Troubleshoot audio playback wizard
• Updating my Realtek Audio drivers
• Swapping out audio cables and speakers

No luck. Just as I was about to give up, I realised:

The volume control dial on my speakers also has an adjustment for Front/Rear speaker balance. A certain small child had obviously 'played' with this while I was away, and adjusted it so that the balance was 100% rear speakers (which aren't plugged in).

So my suggestion to Microsoft is they add a step to their troubleshooting wizard:

- Have you checked that small children haven't fiddled with the front/rear speaker balance setting

Anyway, I thought I'd post this in case it helps anyone else with the same problem.