I use Jamcast by SDS Technologies. It's a similar app, but for PC. However it is audio only. There is a free 14 day trial which requires you to signup to their website and verify your email address, which is what I did and tested out the software. Apart from that the trial really is free, I don't remember having to give my credit card details or anything like that. The website is very clear that the app will cost you £26. (I assume that would be something like $40)
(Disclaimer: I don't work for Jamcast and am not affliated with them or any similar company. I found the software quite nifty and thought I'd share with you guys about it. I would have preferred to link to a more ''neutral'' Wikipedia page instead of their website, but unfortunately there is no jamcast Wikipedia page. If someone knows of a similar app, reply to me and I will edit my post. Free would be best of all!)
PulseAudio works well to stream audio output to a different machine, but I think it's *nix exclusive and kind of a pain to setup. Jamcast is a program I found by googling that seems to fit the bill for windows.
Speakershare also fits the bill and seems dead easy to setup.. but the website is gone and I can't find a working download link.
> PulseAudio runs under Microsoft Windows and POSIX-compliant platforms, such as Linux and FreeBSD.
I never tried it myself, but it looks promising. However, with Windows you might be better off betting on UPnP instead.