iOS 4.2 for Apple TV 2G is now available for download. You can download iOS 4.2 build 8C150 for Apple TV 2nd Gen from the link below. Apple released the iOS 4.2 firmware together with iOS 4.2.1 for iPad, iPhone, and iPod Touch.
This Apple TV 2G firmware update comes with AirPlay that let you stream contents (Videos, Photos, Music) from your iPhone/iPad/iPod Touch to your Apple TV 2G and VoiceOver function.
AirPlay lets you stream digital media wirelessly from your iPhone, iPad, and iPod touch to your Apple TV and AirPlay-enabled speakers. So you can watch movies and photos on your widescreen TV and play music through the best speakers in the house.
Download iOS 4.2 Build 8C150
You can download Apple TV 2G iOS 4.2 firmware from update feature or from the link below and use update button on iTunes to install it on your Apple TV.
For iPhone, iPad and iPod Touches, you can download iOS 4.2.1.