Welcome to the forum.
First, what are the source files in this Project and how did you Import/Capture them into PrE?
Second, what is the location of the Preview files in your Scratch Disk Preferences?
Thank you for a word of greetings...
There are two kinds of source files: (1) AVCHD .m2ts files that I copied from my video camera using its supplied software, plus (2) .MOV files from a photo camera. My first idea was to add all of the capture files into the Project section under Organizer tab, but that caused PE to spend good 10 minutes opening the project. So I deleted all clips from the Project section that were not yet used at that time and instead imported them via GetMedia button (PC files and folders), so that they all showed up under Media. I then dragged certain clips from Media into the timeline.
Now when I look at the Project section, I see all clips that are included in the latest version of the project, but some of them not checked off as "used" (there is no green check symbol). Can this be a reason for their re-rendering? Actually, some of them are not checked off but are rendered...
The .m2ts media files are in C:\Projects\R2009\HDWRITER\..., and C:\Projects\R2009\ is where I placed .prel project file, and therefore Preview folder is also there.
I made one attempt to scratch the original project and copy all clips into a new one, but could not find a way - I can select all, copy, open new project, but then cannot paste.
Thanks much! It is a great software to play with.