HT1600: Apple TV (1st generation): How to update Apple TV softwareLearn about Apple TV (1st generation): How to update Apple TV software
Currently Being ModeratedJan 6, 2013 10:12 AM (in response to 10crossbones)
Welcome to the Apple Community.
AirPlay Mirroring requires a second-generation Apple TV or later, OS X 10.8 or better and is supported on the following Mac models: iMac (Mid 2011 or newer), Mac mini (Mid 2011 or newer), MacBook Air (Mid 2011 or newer), and MacBook Pro (Early 2011 or newer).
Currently Being ModeratedJan 6, 2013 10:14 AM (in response to 10crossbones)
As Winston said, you have to upgrade to OS X Mountain Lion in order to get AirPlay Mirroring on the computer > http://support.apple.com/kb/HT5404 You can purchase Mountain Lion in the App Store, and make a Time Machine backup and/or a clone with Carbon Copy Cloner before upgrading.
If you want to use Lion, you can purchase AirParrot > http://www.airparrot.com