If you want to restore back your HTC Pico Explorer to its original firmware then you need to grab its official RUU updates. Below are list of available Stock ROMs or RUU’s (ROM Update Utility) that can be manually flash or install back to HTC Explorer devices. This can be used to unroot and or restore to official firmware from any customized firmwares.
How to check which is the right RUU for your HTC explorer
You need find out the correct RUU version of your device, each specific build refers the device origins.
To get the RUU version just check the software info in Settings–>About Phone–>Software Version.
Grab it here.
How to install RUU
Installing back your HTC Explorer is a bit risky if you are a noob about this method, but it can be easily done just follow this guide here.
!!!DO NOT RELOCK the bootloader before Step 4 – this will brick your phone!!!
1. download RUU for your device here (check your radio at top the bootloader menu)
2. extract the RUU rom from RUU application
start the ruu application, even if it fails. also start the flashing process, nothing will happen here. search for the ruu logs, for me at c:\ruu_log. in the log (for me in line 191) is the path to the rom.zip that should get flashed. something in temp folder… for me the line looks like this:
3. flash the needed images
in the rom.zip you will find a boot_signed.img, a system.img and a recovery_signed.img. flash all these images with fastboot.
In command line:
fastboot flash system system.img
fastboot flash boot boot_signed.img
fastboot flash recovery recovery_signed.img
4. relock the bootloader
In command line:
fastboot oem lock
5. install with RUU application
now run the RUU application again and follow the instructions.
You are then back on RUU now.