I was served a subpoena for illegally downloading a movie, what should I do?

I was issued a subpoena in the mail from a judge alleging that I illegally downloaded a movie . The date is from over a year ago. The subpoena says that I must get this resolved within 30 days or my name and information are going to be released. I have no memory of this and don't even have the computer anymore. Here is a copy of the document http://docs.justia.com/cases/federal/district-courts/california/candce/4:2010cv04468/232608/7/. What should I do about this?