I've read a property from the registry, and that property has been set properly (I'm using this to check the property value)
<CustomAction Id="Test" Script="vbscript">
<![CDATA[MsgBox Session.Property("MYEXTRAFILESFOLDER")]]>
</CustomAction>
Now I'm just trying to drop a few files into that folder. I can't figure out how to make a File element target a specific directory.