With the release of Windows Vista, some significant changes have been made to the sound controls. The popular Stereo Mix feature has become obsolete and is no longer recommended. Let me remind you that this feature allows you to record sound coming from any application to your speakers. Support for this feature now depends on the hardware manufacturer. How do you record streaming audio now? To do this, Microsoft has introduced a new standard feature that allows you to record from the "Speakers" input. What's the difference between the two?
Stereo Mix is a feature of the sound card driver. It mixes audio streams at the hardware level.
Speakers is a Windows feature. It mixes audio streams at the software level before they get to the sound card.
In light of the above, the situation has changed for the better. Now you don't need to look for a suitable audio driver or change your sound card. All you need is a modern recorder that allows you to use the innovations in Windows.