If you are an proud owner of Google Nexus 7 device and you want to try out latest version of Android Jelly Bean 4.2 on it follow this tutorial to find out how to do that.
For those who already have their tablet roote, do the following:
Step 1: Download the .zip update from this link and unpack it on your Nexus 7.
Step 2: Custom boot into recovery and flash the zip file as usual.
This is the procedure for those who do not have their Nexus 7 tablet Roote:
Step 1: Download the necessary zip file from here. Rename downloaded file into update_nexus7.zip which will be much easier for us to find it later.
Step 2: Now download the Android SDK.
Step 3: Turn off the Nexus 7.
Step 4: Press and hold Volume Down + Power buttons to enter fastboot menu (the one with the green Android robot with open abdomen).
Step 5: Press Volume Up until you reach the Recovery mode and then validate with the power button, you should see the robot lying down with a red exclamation mark.
Step 6: Now press Volume up + Power until you get to the recovery menu.
Step 7: With Volume up button select the “apply update from ADB” and then confirm with the power button.
Step 8: Connect the Nexus 7 to the computer via USB.
Step 9: Install the update with ADB. To do this, enter the following command “adb.exe sideload update_nexus7.zip”.
Step 10: The update will install in few minutes and you are ready to use Jelly Bean on your Nexus 7.
Tutorial Source: DeviceMondo.com