by Hard Reset
Before you buy a new cell phone or new tablet, please try the following procedure to repair your device. First charge your battery, backup your important data if possible and in most cases take out SIM and SD card before 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.!
HTC Tattoo hard reset
Resetting the Phone
Resetting the phone deletes all data, including downloaded applications, and resets the phone back to its initial state—the state before you turned on the phone for the first time.
Important Make sure to back up important data you have on the phone before you reset your phone.
To reset the phone using phone buttons
1. With the phone turned off, press and hold the HOME and BACK buttons, and then briefly press the END CALL/POWER button.
2. Press the ENTER button to begin the reset process.
Tip If your phone hangs or freezes, remove the battery then wait for a few seconds, and then re-install it. After re-installing the battery, turn on the phone.
To reset the HTC Tatoo Tatto phone
1. Press HOME > MENU, then tap Settings > Security > Factory data reset.
2. On the Factory data reset screen, tap Reset phone and then tap