trapple
I am strictly an Elements Windows user but, no bias, Windows is a better choice because of the Windows Only features that the Premiere Elements Mac user runs into. But, one of these days, I need to get a look at Mac to see what it is all about. All that being said...
The critical rule is never move, delete, or rename source media that went into a project after the project is saved closed. When you import media into a project, all you have in the project are copies of the originals on the hard drive. And, the project needs to trace back to those originals on the hard drive location where they were when they were imported into the project.
Life Saver at times: Adobe Premiere Elements 11 * Archiving projects
If you delete the previews files, you can re-render the Timeline involved if needed to get the best possible preview in the Edit area monitor. This is just a preview matter.
If you delete the conformed audio and conformed video files, the program automatically generates new conformed files when and if the project/program decides they are needed.
There may be times, when you need to get rid of the preview files even if there is the potential for having to render the Timeline again. They can pile up fast and you may need the space.
Setting up a folder/file setup for each project will be of benefit when comes time to delete a particular project and all its related non source media assets.
The default is all files automatically going to hard drive save location and you sorting through Adobe folders for the name of the project that you want to delete.
Please review the above. If any questions or need clarification, please ask.
Thank you.
ATR