Q: I have a MacBook Pro 15inch Mid 2010 which I have upgraded to Mountain Lion. Is there anything I can do to get Mirroring?

Welcome to the Apple Support Communities

AirPlay Mirroring is only compatible with Early 2011 and newer MacBooks Pro, so you can't use it in your computer. Read > http://support.apple.com/kb/HT5404

However, you can use a third-party application to mirror your Mac into the Apple TV, as AirParrot > http://www.airparrot.com

About AirPlay and Airplay Mirroring

AirPlay Mirroring requires a second-generation Apple TV or later, 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). For non-qualifying Macs you can try using Air Parrot.

Several Apple Articles Regarding AirPlay

Apple TV (2nd and 3rd gen)- How to use AirPlay Mirroring

How to set up and configure AirPort Express for AirPlay and iTunes

About AirPlay Mirroring in OS X Mountain Lion

iTunes 10- About playing music with AirPlay

Troubleshooting AirPlay and AirPlay Mirroring

Using AirPlay

Thanks to the $15 Beamer, AirPlay streaming is still possible on Macs  that do not support Airplay and mirroring.

Another solution is the Air Parrot.

You are welcome

Hi,

I have a late 2011 macbook pro 13"(I checked the serial number). osx 10.7.5. Apple tv 3 (md199LL/A) version 5.2.1. and i still dont' see the airplay symbol at the top of my screen. I can airplay from itunes, but not mirror my screen. Any ideas?

yes, i have thanks. I do have a computer that this should work on, i have read the apple support page and it's not working. I tried parrot, it's great, but i'd rather not pay for a feature that should already be there. thanks.