Windows 7: Audio only works through headset

Since upgrading our Fujitsu Siemens Amilo PI1505 to Windows 7 in the past few days I've only been able to get sound through a headset and not through the speakers. Not particularly having a clue what to do I've tried installing the original audio drivers but can't do so as Windows tells me that more up to date drivers are already installed. Details below:

Driver Provider: Microsoft
Driver Date: 13/07/2009
Driver Version: 6.1.7600.16385
Digital Signer: Microsoft Windows

Any ideas on how to resolve this problem and if indeed it is a driver issue any ideas how I can get the old driver to replace the new without Windows reinstalling the latest ones on Restart.

Any help appreciated.

Hi SteveBC

Check your speakers set up.