Is there software to mirror a Windows PC via AirPlay? I would like to mirror my Windows PC to my Apple TV via AirPlay. I've found a few options which enable Windows Media Player to receive video via AirPlay. I've also found an application named Airfoil which allows you to stream audio from Windows. I know that the beta of Mountain Lion supports AirPlay mirroring, but is there a Windows option?
I use a program called AirParrot to mirror my Windows PC to my Apple TV (third generation). There is also a version that works on Macs.

Note that the ability to mirror a Mac to an AppleTV is a new feature of OS X Mountain Lion.