You may have installed the wrong audio driver.
The same model Lenovo can have different types of network, video and audio drivers and unless youknow exactly which one is installed in your Lenovo, you need to download allthe drivers and install each driver until you find the right driver.
When you download thedrivers, write down the device driver and it's file name so you have a recordof which driver you are installing and which directory the unzipped files arelocated on your hard drive.
Go to the IBM/Lenovo WEBsite - support/download page and download the latest Windows XP or Vista devicedrivers for your model computer, Use this link: -
You can download thevarious drivers and then you click on and run the various driver files, theywill then unzip and expand into a sub folder on C:\drivers Then install thevarious drivers from this folder (run the set-up file).