How can i mirror my mack if its 24-inch, Early 2009 running lion OS X 10.8.4?

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Read > http://support.apple.com/kb/HT5404 In the case of the iMac, AirPlay Mirroring is compatible with Mid 2011 and newer iMacs, so you can't use it in your Mac.

Instead, there are other applications that give you the option to mirror the iMac screen onto the 2nd or 3rd generation Apple TV you have. Some apps are Beamer and AirParrot, and work in the same way as AirPlay Mirroring. You won't have any problem with them