Modify an installation package

Hello,

I manually created an installation package from the 12.1.2 file downloaded via fileconnect.  However when I extracted the files from the zip from fileconnect, I accidently left out a few folders.  I would like to rebuild the installation package I created, so that it will contain all the files it's suppose to. SEPM won't let me delete or modify the package I created because it is "the latest version".  Is there any way around this?

Thank you,

Steven