"I have this folder which is 80GB"
This an iMovie 10 library. If you delete it you will loose all the contained events and projects but the iMovie application will not be affected.
"I wanted to do a clean/fresh install of imovie"
Why? It seems from the above that you do not want to have to reinstall iMovie but just delete all your current events and projects. I'm a bit confused.
"Ive already deleted all the event and project files and folders"
if you mean the folders called "imovie Events" and "iMovie Projects" these belong to iMovie 9 or earlier.
Geoff.