I've created a profile to asp.net forums which has my full name as username and I don't want it to be displayed on my every posts. If I can change username then good, otherwise I want to delete that profile.
Contact their support.
You can edit your profile name on this page It is linked at the top right of the forum pages when you are signed in.
You cannot change your username nor can you directly deactivate your account according to this: http://forums.asp.net/t/1933703.aspx
I tried the contact link at the bottom of the page takes you to a maze worthy of phone-tree envy.
I was only able to deactivate my account by posting a message in the "Feedback on this website" forum: http://forums.asp.net/188.aspx/1?Feedback+on+this+website and wait for a moderator to handle it.
You can submit an ASP.NET site operations help support ticket from the Contact Us page.