New
#11
The only way I know to make it show up is by right clicking in the white space to show "disabled and disconnected devices". Apparently, you've already done that.
It's no accident that Microsoft forces you to do that rather than showing disabled and disconnected devices by default. It's intentional. You didn't see that on XP. It's done in an attempt to make it difficult to record what you hear due to pressure from certain organizations that don't want you to do that. Microsoft has yielded to the pressure.
Some motherboard sound chips DO support Stereo Mix on Windows 7. Mine does (Realtek). Others don't. The difficulty has arisen only in the last few years.
It's a function of the sound card drivers. Either they support Stereo Mix or they don't, subject to whatever workaround you or others can dream up.