Samsung Galaxy Tab 7.7 hard reset

Personal Data
Factory data reset
Use Factory data reset to return your device to its factory
defaults. This setting erases all data from the device, including
Google or other email account settings, system and application
data and settings, and downloaded applications. It will not erase
current system software and bundled applications, or files stored
on an installed memory card, such as music or photos.
1. From a Home screen, press the Menu Key ➔ Settings ➔ Privacy.
2. Touch Factory data reset, then follow the prompts to perform the reset.

Samsung Galaxy TAB P6210 hard reset using keys

1. With the Samsung Galaxy TAB 7.0 turned off, press and hold the VOLUME UP button, and then briefly press the POWER button.

Note: If you see  "Downloading" on the screen with an Android shoveling you pressed the wrong Volume key. Turn off and try again.

General advice: Before you buy a new cell phone or new tablet, please try the following procedure to repair your device in a software way. First charge your battery, backup your important data if possible and in most cases take out SIM and SD card before doing factory reset. It is impossible to recover your data after doing a hard reset, so online backup is always important. For all of your data, a backup should be done on an external device, hard drive, raid system or media. With or without insurance, if your cell phone lost, damaged or stolen at least your invaluable data is backed up in a safe place. If you are about to sell your phone and you want to wipe your personal data, or if your phone affected with virus you have to do a hard reset. In some cases, you can delete the forgotten password or lock pattern from your device as well. All information is for devices with stock based ROMs. If you are using rooted device, always back up your EFS folder first, containing your IMEI info, etc.! Please also note, that a hard reset operation will not unlock your mobile phone's SIM lock or network lock, but it will remove the unlock pattern, remove the user password or PIN password (NOT the SIM card's 4 digit PIN code). Also note that the firmware version will not be affected in any way, it will not be downgraded, it will remain the same you are using and if you have rooted your device, root privileges remain also unaffected.