factory reset - How to reinstall android to the fresh stock?

I have recently bought a used HTC Evo 3D from the internet. The phone itself is in perfectly working condition and the software is in its original state; that means it's not rooted, it's not running any custom rom and it's not branded.

However, the previous owner seems to have installed many apps from the market, the launchers are kinda different and generally the phone is very 'customized and seems sloppy.'

My question is: How do I get the device to its original, fresh, stock state? I don't want to install a custom ROM, I want to have the original android provided by the device manufacturer.

I know the device has the "factory reset" option in the menus, however I don't know what it really does and how thorough it is.

Wiping the phone and installing the system from scratch would be the best option for me, however, I don't know whether it's possible.

What are my options here?

Notes:

• I know what rooting is



• I know what custom ROMS are


• I can root the device if necessary, but I don't plan on doing so if not necessary


• Android 4.0 gets an official release for HTC Evo 3D soon - does this change anything related to what I need/want to do?

Answer

If it's not rooted and not running a custom ROM, a factory reset will reset everything back to stock and wipe the internal SD card. If you also wipe the external SD card, you will have a clean slate.

Checkout Chapter Update and Reset, Section Resetting HTC EVO 3D, (Page 209) of the manual: http://www.htc.com/managed-assets/support/user-guide/user-manual/htc-evo-3d/110803_ShooterU_HTC_WWE_UM.pdf

Quoting the manual:

Resetting HTC EVO 3D

Do a factory reset to return HTC EVO 3D to its original state before the first time you turned it on.

If you’re passing HTC EVO 3D on to someone else or HTC EVO 3D has a persistent problem that cannot be solved, you can perform a factory reset (also called a hard reset). Factory reset is not a step to be taken lightly. It’ll permanently delete all your data and customized settings, and will remove any applications you’ve downloaded and installed. Be sure to back up any data and files you want to keep before you do a factory reset.