search under device "desire s", version "4.0"..got RUU for WWE region..however the filename said its EU region..

http://dl4.htc.com/RomCode/Source_and_Bina....110_275068.zip

No, u just connect your phone to your computer and run the ruu... 4ext recovery is only for custom ROM. U can't flash official rom with 4ext recovery...

The RUU ends with .exe extension. So u only need to double click it and follow instructions. The RUU seems good to me. But if your phone is unlocked using revolutionary or alpharevx, you better dont run it. "Running the RUU will lock your phone".

Regarding people who having hboot version 2.xx.xxx..... U can go download the unlock bootloader from the htcdev.com... Once unlock, u can flash custom ROMs and stuffs but remember, u need to flash the boot.img for those who use htcdev.com unlock bootloader....

for those who unlock their phone using revolutionary or alpharevX.... u dont need to flash boot.img... but this is only for Hboot version 0.98.xxxx (Old version). This is much more simple and more convinient flashing custom ROMs....

Hboot with higher version is more troublesome and requires 1 or 2 more steps when flashing custom ROM. Please refer to the custom ROM thread for more info before flashing.

Those who unlocked their phone, I recommend you to use 4ext recovery, which is free and stable. Download the free recovery here: http://4ext.net/

U need to follow those guides on XDA forum, follow them step by step, it's on the General section. I've made a guide for all these.

Did u unlocked it? If yes, u cant do that.... power off your phone, take out your battery, insert back, and press volume down and power button at the same time, it will boot to your bootloader.... On that white screen, u will see if your phone is unlocked or locked....
Note: you dont need to take your battery out if your fastboot settings is set of "OFF".

If your phone is unlocked its better to just flash the custom official ROM... But u need to upgrade your hboot if your version is 6.xx or 0.98.xx. There are tons of guide on the XDA forum, read those, its really helpful... or check my thread to update your hboot under the General Section...