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.!
Google Nexus ONE hard reset
You can do a hard reset from the menu here or with buttons see below
Applications SETTINGS > PRIVACY > FACTORY DATA RESET. This will ERASE ALL DATA on GOOGLE NEXUS ONE!
TAP RESET Phone than EREASE EVERYTHING. NEXUS 1 WILL REBOOT!
Google Nexus ONE hard reset with buttons / keys
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IF YOUR NEXUS ONE SCREEN FROZEN
Power off Nexus ONE remove/reinsert battery if power button not responding.
Hold down VOLUME DOWN and push POWER ON button for one sec. Release buttons.
You will see a boot menu HBOOT with various options.
NEXUS ONE FASTBOOT, RECOVERY, CLEAR STORAGE and SIMLOCK menu options.
Select with Volume up / down keys and Enter option with POWER button.