1) Download latest Sony Update Service...Actually i own a Xperia S. I flashed Fera JB v2 on my friend's x10 almost 3 months back. Now he wants to get back to stock. So i am not much familiar with x10 forum. It would be really appreciable if u can point me to a kernel for locked bootloader with xrecovery.
Thanks
2) Install Sony Update Service...
3) Run Sony Update Service...
4) Follow whatever inside the Sony Update Service...