Tages is usually found on pc games. It should have nothing to do with Audacity.
In Win7, click on Start-->Control Panel-->Sound. Click on the Recording Tab and see if Stereo Mix is listed. If not, right click in the window and put a check mark in Show Disabled Devices. Stereo mix should show up and you can enable it.
I'm not sure this is the solution, seeing that I'm still learning Win7, but it might work.