With the new modded firmwares we have ability to run .lin files and even .sh files. So there is no longer need for mpkg software installation - you can directly extract the .lin file from it with winrar or winzip.

Many people are recently asking how to delete their installed MPKG programs from the Motorola ROKR E2 menu (there is install function, but not delete function). Here is a brief tutorial:
1. Assuming that you are installing the mpkg in the memory card mode - go open /.system/java/CardRegistry file from your Secure Digital card with Notepad or other simple text editor
2. Remove the line with the name of the application
3. Go to /.system/QTDownLoad/ - you will find the application itself there. Delete it in order to free up some space