It will remove all the data ,contacts and apps that you installed
First Remove the battery, wait for a few seconds (15 to 20 seconds), then reinsert the battery.
After that Press and hold VOLUME DOWN button, and then briefly press POWER button.
Next Wait for mobile screen with the three Android images to appear, and release the VOLUME DOWN button.
Press VOLUME DOWN to select FACTORY RESET (All data will be deleted), and then press the POWER button.
Hard reset done on your HTC Android mobile phone.
Push the Power button to turn on the device.
Then from Main Menu go to Settings and tap Backup & reset.
Next choose Reset phone and select Erase all data.
Tap OK to confirm your choice.
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Restore Hard reset will set your phone in origional factorry settings. It will remove all the data and apps that you installed. Your contacts will be removed and you have to add them again.