Here's a step by step instruction on How to Hard Reset or Factory Reset the HTC 7 Mozart T8699
If the device becomes unresponsive or sluggish when opening some applications, try to restart the phone and observe if that helps.
To restart the phone, simply turn it off and back on again. If pressing and holding the POWER button doesn’t work, then remove the battery, wait for a few seconds, reinsert the battery, and then turn the phone on.
In case the phone has a persistent problem that cannot be solved, the last option is to do by a way of factory reset.
Performing a factory reset via settings
The most convenient way to do a factory reset is via the phone settings.
Factory reset is not a step to be taken lightly. It will permanently delete all your data and customized settings, and will also remove any apps you’ve downloaded and installed on the device.
Please make sure to back up any data and files you want to keep before you do a factory reset.
Restarting or factory resetting your HTC 7 Mozart T8699 phone (soft reset) 1. From the home screen, swipe left to expose your app list
2. Select Settings
3. Scroll down and select About
4. Select Reset your phone
5. Select yes to confirm, then Select yes to confirm again
HTC Mozart T8699 factory reset (hard reset)
Performing a factory reset using phone buttons combination
If you cannot turn on your phone and cannot access the phone settings, you can still perform a factory reset by using the buttons on the phone.
1. Turn the device Power OFF, if the HTC Mozart T8699 is Frozen: press and hold the VOLUME UP and DOWN buttons, and then briefly press the POWER button.
2. Wait for the instructions to show on the screen on how to do the factory reset, and then release the VOLUME UP and DOWN buttons.
3. Just follow the step by step instructions onscreen to factory reset the phone.
It will then reboot and the HTC 7 Mozart will now be wiped and you'll be left with a factory fresh phone.