[One (M7) Q&A, Help & Troubleshooting] Sib64:
It's a part of my guide, if you want you can try it. Sure I'm not Mike1986, but my guide is functionnal ;)

[GUIDE] Download HTC One M7 RUU - Restore back STOCK​

Find your HTC One M7 Rom Update Utility (RUU) is very useful if you need to restore back your device to Stock after any modification you’ve made. If you have rooted your One, unlocked its bootloader, installed custom recovery and roms and finally you want decided to getting back to official firmware and then to get or accept future OTA updates again. It’s the best way to restore back your device to Stock.

Coming back to stock is also useful if you have some bugs (for fixing it), Bootloop, stuck in boot screen logo and freeeeezzziiiinnnngggg, etc....

But before to going back to stock, you need to know :

Your bootloader will never be “LOCKED” again !!! You can’t restore it, just RELOCK it.

The “TAMPERED” text in your bootloader will only disappear after the flash of your RUU.​

1 - Where I can can find the right RUU for my HTC One-M7 ?

First, you need to download the RUU that matches your device according to what carrier you have, hboot version, and baseband. The RUU will not run if it doesn’t match your device.

If you don’t know your One M7 variants, go to see the end of the post,

and this tread - HTC One variants [U/UL/WL]

But first download and install the necessary files prior to execute this properly. If you have already installed those files, just check theirs.

HTC Sync

(Windows only)

Java Runtime Environment

.

Android SDK | Android Developers

.

Platform tools

Fastboot files

2 - Checking HTC One hboot and overall firmware version

If you already have this installed on your computer then proceed to checking your device info.

To find the correct firmware info of your device (modeid and cidnum), just simply run your device using the below fastboot command.

Hold the power button down until the phone power off.

Press Volume Down and Power to start the device into Bootloader mode.

Use the Volume buttons to select up or down. Highlight Fastboot and press the Power button.

Connect the device to the computer via a usb cable.

Run command prompt. ( Start > Run > type CMD).

C:\fastboot>fastboot devices

C:\fastboot>fastboot getvar all

You can read the whole logcat and get your device correct hboot and baseband version.

Download the right RUU for your HTC One from this thread :[COLLECTION] HTC M7 RUU, OTA, and Stock Nandroid Downloads

3 - Running HTC One M7 RUU

First make sure that your battery is fully charge 100%

If you are ready, you need to re-locked the bootloader before to going back to the RUU

Set the phone in fastboot mode (select fastboot from hboot menu), then plug-in USB cable.

Run the command prompt window, go to your fastboot directory

Enter the following commands:

fastboot devices

fastboot oem lock

It will then prompts you into a security warning and then relock your bootloader.

Now, you can boot your device into fastboot mode again,

Run the RUU.exe once your device is in fastboot USB mode.

Simply follow the RUU prompts, just wait and don’t unplug the phone until completely finishes.

The phone will reboots once completes and finally your phone should be on stock again.

RUU VARIANTS:

x.xx.61.x - Orange UK (United Kingdom)

x.xx.65.x - Orange CH (Switzerland)

x.xx.69.x - Orange PL (Poland)

x.xx.73.x - Orange FR (France)

x.xx.75.x - Orange ES (Spain)

x.xx.110.x - T-Mobile UK (United Kingdom)

x.xx.111.x - T-Mobile DE (Germany)

x.xx.112.x - T-Mobile AT (Austria)

x.xx.113.x - T-Mobile CZ (Czech Republic)

x.xx.118.x - T-Mobile PL (Poland)

x.xx.161.x - Vodafone UK (United Kingdom)

x.xx.163.x - Vodafone FR (France)

x.xx.165.x - Vodafone IT (Italy)

x.xx.166.x - Vodafone CH-DE (Switzerland - Germany)

x.xx.168.x - Vodafone GR (Greece)

x.xx.169.x - Vodafone AT (Austria)

x.xx.206.x - O2 UK (United Kingdom)

x.xx.207.x - O2 DE (Germany)

x.xx.401.x - World Wide English

x.xx.415.x - Arabic (UAE/Middle East)

x.xx.468.x - Turkey

x.xx.497.x - Morocco

x.xx.498.x - WWE Brightpoint US (United States)

x.xx.531.x - T-Mobile US (United Kingdom)

x.xx.666.x - Bell Canada

x.xx.707.x - Asia WWE (World Wide English)

x.xx.708.x - Asia HK (Hong Kong)

x.xx.709.x - Asia TW (Taiwan)

x.xx.720.x - Asia (India)

x.xx.728.x - Virgin AU (Australia)

x.xx.751.x - Chunghwa Telecom (Taiwan)

x.xx.771.x - Hutchison 3G UK (United Kingdom)

x.xx.841.x - Telsra WWE (World Wide English)

x.xx.862.x - Voda-Hutch AU (Australia)

x.xx.901.x - TIM IT (Italy)

x.xx.911.x - SK Telecom (South Korea)

x.xx.980.x - Optus AU (Australia)

x.xx.1400.x - HTC China

x.xx.1403.x - HTC China CMCC (China Mobile Communications Corporation)

x.xx.1540.x - HTC One U.S. Developer Edition

Thanks to mike1986 for this list ;)