You can petition the court for a legal name change. You follow all procedures required in your local court, such as publishing in a local newspaper. Attend a court hearing with proof of proper notice and get the judge to sign. When all the legal mumbo jumbo is done you have a Decree Changing Name and can have everything changed to conform. Birth certificate, social security card, passport etc...
It's pretty easy to find the information for your area online.

*This is just basic info. There are several more steps involved but just wanted to give the watered down version here.

Last edited by Islenutt; 05/12/09 12:25 PM. Reason: added info