The eMusic - 50 Free MP3 offer is somewhat dubious because if you don't read the agreement, you will be charged for money at the end of the trial period. The software is distributed with Winamp but the support for Winamp has been discontinued. You should simply uninstall the software since it isn't available anymore.
However, if you want to delete the account on Answer Informer, there is the support contact form you can use to get in touch with the admins of this website. I believe they will help you to delete the account.