This type of question should really be asked in the Feedback on Developer Exchange forum or by email the site administrator directly, I'm sure the people that recieve these messages as part of their newsgroup services don't want read about DE specific problems.
That being said, click on "My Profile" in the top right corner of all NI web pages. From there click on "Modify Profile". You will see a box containing your information including your "Alias", click on edit and change your alias.
Brian