Happily this is easily achieved, but it has to be done backwards.
Delete iMovie 11 (just drag it to the trash). Now install iMovie 6 from the iLife 6 install disks.
Now re-install iMovie 11. This automatically moves iMovie 6 into a folder it creates in your Applications folder called iMovie Previous Version.
Then reinstall iMovie 11.
Now you have them both, and you can have both in the Dock as well.
Alternatively you could try this method, suggested by poster Uitech:
Open a terminal and type "touch /Library/Preferences/com.apple.iLife08.plist"
Install iMovieHD6 from the iLife 6 install disk.
This works with both Leopard and Snow Leopard Macs.
No, I do not have iLife 8. The terminal command you had referenced was "touch /Library/Preferences/com.apple.iLife08.plist" and I have no library file like that apparantly because I do not have "08." The "touch" reference was yours. I am using a MacBook Pro.
My big concern in wanting to also have iMovie 6 is that I do not cripple iMovie 11 or lose previous work done in "11" which is in the iMovie 11 "iMovie Events" and "iMovie Projects" folders.
Hi Klaus. This is the only thread I could find that was the same as my question. I"m running Lion and I would love to have iMovie6 living harmoniously beside '11, but I don't want to lose my projects and events in '11 (they seem to be tied to the '11 interface, without separate project files in finder, much like new iPhoto). Will that touch permission work on LIon? I've heard some very stern warnings about doing that kinda stuff in the terminal....like I could really screw up my system. Thanks in advance for any tips!!