Hy, this is a copy from another forum, its work for me
.....Open start, than Controll panel, Sound, Than recording( My OS is set to norwegian so i don't know exactly the name of the menu, but it is the one in the middle and it has options with recording) In the recording window there will be a few options, right-click in the background of the window and press "Show offline units" (again i have norwegian OS don't know exactly what it says" press "Show offline units and you will have a new option called something like Stereo Mix. Enable Stereo Mix, and hopefully it will work.....
With "Audio CD", make the same thing.