Hello Purator,
I think you have to create a link to the organ file and move it to the Autostart-Folder. To Do so, right-click the *.organ-File and then click "Create Link" (or whatever comes close to this, I only have a German version of Windows). You then rightclick the newly created file (should be like "Link to xxxxxorgan.LNK") and click "Copy". Then click "Start" and goto "All Programs". You should find a Folder called "Autostart" there. Rightclick in it and then click "Paste". Now on Startup, the Organ file should be loaded.
That's not actually quite correct - v1 didn't use Windows DDE/file associations for its .organ files. If I recall correctly, you could pass the name of a .organ file on the command line (a property of the shortcut used to launch the application), although I have to stress we definitely no longer provide any support for versions of Hauptwerk prior to v4.
P.S.: So if I understand correctly, the Free Edition is not allow to be played "in public", but what if I buy the Advanced Edition for my home, and use it almost always there but want to play once at a church (e.g. to show them what it can as mentioned on the "How to suggest HW..."-Thread, or to replace the way-too-small-keyboard for the christmas-service). Do I have to buy a public-installation-licence for this one event, or is it ok as it is a unique event?
It's no problem using a Hauptwerk Advanced or Basic Edition licence in public on an occasional basis with portable/temporary installations. It's only if you Hauptwerk is kept installed on a permanent or semi-permanent basis in a public place that you need a public installation licence.
Best regards, Martin.
Hauptwerk software designer/developer, Milan Digital Audio.