I have Windows XP Professional and needed to livestream the speakers audio for my painting streams, but the recommended 'Speakers Audio' input option under Audio was not showing up for me. (The only input option was my Creative Sound Blaster PCI, and it did nothing.)
I tried installing an older version of Procaster
and it solved the issue - I am now able to choose Speakers Audio as an input version and both audio and video show up fine on my stream.
I don't know if it will work for everyone else with a similar problem, and obviously it's of very limited use to those who want to audiomix input from their speakers and mic, but it's something, at least. So I thought I'd put this out here.
I really hope the developers release a new version that's as advanced, driver compatibility-wise, as the outdated one. :P