Sure, I linked to a in browser Linux emulation too. But both I think Windows isn't really what you want, and the Linux emulation has no network access.
They both also rely on emulating an x86 system. I think what might be interesting is something that creates an in browser process model, possibly POSIX compliant. To which you could target applications, critically I think they'd need network access.
http://ascii.textfiles.com/archives/4546