Like I said. Goto the PACKAGES directory
In there you will find another directory named BACKUPS
Now let's assume, for the sake of this tutorial, that the last mod that you installed was "PM On Registration".
You will need to locate something like this in the Backups directory "2010-01-26_before_PM_On_Registration_1-0-2.tar.gz" The numbers at the front of the filename is the date that the mod was installed, So yours should be different.
Download that file to your desktop