When you originally purchased this utility online, you should have downloaded a file with which to install the software. If you did not keep this file and need to re-install the utility, then you should contact the developer/vendor and explain your change of e-mail address situation. The vendor most likely will simply update their records, such that you [would] be able to go ahead and download the installer a second time....
note: if you are in fact able to download the utility/installer a second time, make sure to keep the file backed up in a secure location...