Deleted iMovie by mistake, need old version installed
I run a MacBook OS X 10.7.5. I was having mega problems with iMovie crashing all the time, so in desperation I deleted the iMovie App with a view to instantly reinstalling it. HOWEVER, I can't install it as I need an older version of iMovie (version 8 or 9 I think) and the newer version (10) won't install as it is incompatible with the OS. Can anyone suggest anything to me as to how I can get iMovie back again, please? I don't have disks as the laptop was secondhand and already had iMovie installed. Many thanks!
iMovie 10, Mac OS X (10.7.5), Need iMovie 8