HTC - Restore Backup/Stock ROM

Methods for returning back HTC One X to stock ROM from any custom ROM

Method 1
Go to: bootloader / fastboot mode: (refer above guide)
1- flash a stock recovery.img

• fastboot flash recovery recovery_signed.img
• fastboot reboot-bootloader
• fastboot erase cache

2- flash a stock boot.img

• fastboot flash boot boot_signed.img
• fastboot reboot-bootloader
• fastboot erase cache

3- re-lock bootloader

• fastboot oem lock
• fastboot reboot-bootloader
• fastboot erase cache

4- run/doubleclick RUU and follow instructions.
Grab the stock boot.img & recovery from : xda-developers.com
install stock rom of your CID-fastboot oem readcid (to know your CID)
-all roms are based on x.xx.401.xx , so you need to download the right RUU(that matches your CID) and extract rom.zip to cook a stock rom for you
-flash custom stock rom(extracted and cooked from right RUU) on custom recovery
-fastboot flash boot c:\boot.img (flash stock kernel that’s inside custom stock rom boot.img file)

• RElock the bootloader (you can allways unlock)

-fastboot oem lock

• Right RUU file for your CID
• put your phone on fastboot (it will not boot because you have a custom rom on a locked bootloader)
• now you can run the RUU exe file and upgrade your phone

Method 2

• Extract the rom.zip from RUU of your CID (google how extract ruu.exe)
• fastboot oem readcid (to know your CID)
• Extract boot.img, system.img, signed_recovery.img from rom.zip
• Flash
• fastboot flash recovery signed_recovery.img
• fastboot flash boot boot.img
• fastboot flash system system.img
• fastboot erase cache
• fastboot oem lock
• Power on the phone
• Run the RUU exe file (of your CID) and upgrade your phone

Method 3 (like Method 2, but we dont need to flash the system) (thanks to EddyOS)

• Extract the rom.zip from RUU of your CID (google how extract ruu.exe)-fastboot oem readcid (to know your CID)
• Extract boot.img, signed_recovery.img from rom.zip
• Flash-fastboot flash recovery signed_recovery.img
• fastboot flash boot boot.img
• fastboot oem lock
• Run the RUU exe file (of your CID) in fastboot modeFlash a ROM and boot image based on 1.26 (e.g ARHD 2.1)
• Clear fastboot cache Code:
• fastboot clear cache
• Boot your phone
• Charge you phone completely
• Download stock recovery
• Flash stock recovery Code:
• fastboot flash recovery endeavoru_recovery_signed.img
• Relock bootloader Code:
• fastboot oem lock
• Run your required RUU

Restore

• Reboot the phone into Recovery again
• Go to Backup & Restore> restore> Choose the backup folder or stock folder extracted. 

Notice

CWM NAND: fastboot flash boot path/to/boot.img
TWRP NAND: fastboot flash boot boot.emmc.win

source:XDA and XDA-Developer