Samsung P7100 Galaxy Tab hard reset

Your device freezes or has fatal errors
If your device freezes or hangs, you may need to close programs or reset
the device to regain functionality. If your device is still responsive but a
program is frozen, close the program using the task manager. If your device
is frozen and unresponsive, press and hold [POWER ] for 8-10 seconds. The device
will reboot automatically.
If this does not solve the problem, perform a factory data reset. In Menu
mode, select Settings → Privacy → Factory data reset → Reset Tablet→

Samsung GT-P7100 Galaxy TAB hard reset with keys

With the Samsung Galaxy TAB turned off, press and hold the VOLUME UP button, and then briefly press the POWER button. In recovery menu select wipe data / Factory reset using Volume button and confirm with power key.

Samsung GT-P7100 Galaxy TAB ODIN mode / firmware update mode

To put your tablet in ODIN mode press Volume down + power (on some models + home)
Note: If you see  "Downloading" "Do not turn off target" on the screen with an Android shoveling you are in ODIN mode. In this mode you can connect your device to PC / laptop and update the firmware, or download (upload) a custom binary.

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.