I believe the new iMovie will install over the old one or overwrite files upgrading the older version. What you should do is make a backup of the older version first. You should be making backups anyway with Time Machine.
What it comes down to is if you like iMovie06 so much, then don't upgrade to the newer version.
I don't like iMovie6 "so much," it just has a couple of things I like about it. Such as some of the themes, that aren't in the new one. The new one integrates with Youtube better, I think.
With some of my other software (not apple software, but third party), if I renamed the original version, the new versions didn't replace it. All it was doing was overwriting files with that name. So I'm wanting to find out from someone if Apple software works the same. If the new iMovie will just overwrite the file called iMovie, so that if I rename the old one iMovie6, hten maybe it won't overwrite it.
Also, I have 3 different backups going -- Time Macine duplicates to 2 different drives, and Time Capsule gets a 3rd backup. So I think I'm good in that department. And backing up the old iMovie wouldn't do me much good, I want to USE it, not store it.
