Currently Being ModeratedFeb 12, 2014 2:39 AM (in response to brigittegreece)
Yes it is safe provided you have a backup.
If you are using iMovie 9 you can keep your iMovie Projects and iMovie Events folders at the root level of any Mac - formatted directly connected (not network-connected) hard drive. You can even have them on more than 1 drive.
For details see:
iMovie 10 library packages don't have to be at root level. For details of consolidating and moving see:
The actual iMovie applications have to be in the applications folder of the startup drive.