I tried to download hacks. I could not do it.

There is a form at that page:
http://www.vbulletin.com/members/vbulletin.org.php

What should i write there?

I tried with my vbulletin user name.
It said blur is not a valid username

?
(I'm a vbullettin customer)

You need to go to this page and enter your username, to show you are licensed. (you will need to use your customer number and password to access that page)

I've already show i am licensed.
See my post. You showed same page.

There is a text like that and 3 textbox / saveusernames

Home > Priority Forums Support
We allow you to enter up to 3 usernames per license here, which are designated to receive priority support on our community forums. These users should be people entrusted to work on your vBulletin license. If you request support and your have not registered that username here, then we may ask you to identify yourself. Additionally, adding your username here will allow you to access certain customer-only features


When i try to type my username and push saveusernames
It gives me error.

What error?

at that page enter the username bayblur as its the username your using on *these* forums which you have to enter