SHOWREADME Problem

Hi all. I have

!define MUI_FINISHPAGE_SHOWREADME "$INSTDIR\Readme.txt"

In my script, and for the life of me I cant get the Readme.txt file to open when 'Finish' is pressed. Im not that adept with scripting NSIS yet, and have been using HMNIS Edit to tackle this. Any help would be much appreciated!

You have to extract this file during the installation process.

I am, and have verified that the file exists in the $INSTDIR.