You are communicating just fine.
Let us see if we can get to the core of the Premiere Elements 12 performance issues that you mentioned.
1. Please remind me if you have installed the 12.1 Update for 12. If you have not installed it yet, please do so using an opened project's Help Menu/Update.
2. You say that rendering helped previously. It could be that you have a pile up of preview files in the Adobe Premiere Elements Preview Files Folder in the Adobe Folder.
So let us explore that idea. Please go to that folder and see how much you have in it. (The default is Libraries/Documents/Adobe/Premiere Elements/12.0
Every time you do the Timeline rendering of a clip, the project automatically generates a preview file which is stored on the hard drive at the location that you designate in preferences.
Edit Menu/Preferences/Scratch Disks and the VIdeo Previews choice. For SD project, the file is DV.AVI and for the HD project, the file is MPEG2.mpg (this is the case if the file rendered is a video or a still). Also check out the contents of the Media Cache Files Folder for pile ups of conformed audio files.
The exact location of preview files and conformed audio files (Media Cache) can be found under Edit Menu/Preferences/Scratch Disks.
Also, go to Edit Menu/Preferences/Media and its Media Cache Database area and hit the Clean button to get rid of pile ups of conformed video files.
3. In the quest for computer clean up, you can consider a run through with the free ccleaner product.
Please let us know what you found and if a clean up improved the performance of computer and Premiere Elements? Based on your reply, we can
decide what next.