Currently Being ModeratedNov 3, 2012 4:15 PM (in response to AppleMan1958)
I have several times moved project files among different folders. As long as you keep them in your "iMovie Projects" folder tree you should be all right. You will have to restart imovie for the moves to take effect in the project browser.
Now, moving to another disk! That could easily be a problem. But moving project files won't clear up much space.
You can, however, look for this in the iMovie help:
Copy or move a project to an external hard disk
You can copy or move your iMovie video projects to a compatible external hard disk. Moving or copying projects is useful if you want to work on a project using another computer that has iMovie installed, or if you want to free up space on your computer’s hard disk.
Well, it's in iMovie '11, at least. Maybe not in '09; I don't know. And it's under "Organize video > Ogranize projects".