That tutorial is for jailbreaking only. I says nothing about "unlocking" the phone....and anytime you reload a firmware it is going to relock your phone.
There isnt currently a way to "unlock" 2.1 on WinPC until Winpwn updates.
Check out this thread. You may be able to find a 2.1 unlocked firmware file that will work for you. Make sure you read through the thread good and follow the instructions.