Randomly can not open .prel file in Premiere 15

To add to what Steve said:

A project file (.prel) is just an instruction set that stores all of the information about the edits and effects applied.  It is use to create a finished video by exporting (Share is the Premiere Elements terminology for that).  The exported file is the file that is used to view the finished product (such as an .mp4 file).  It is also a media file.

A media file is file that you can play in a player or import into a Premiere Elements project to edit.

I'm using Adobe Premiere Elements 15-Video. I import an original 8mm movie in MP4 format to edit. When finished I select File>Save As and a screen pops up and I select the location for storage and I give the video a name after File name:. The default file type is: Adobe Premiere Elements Project (.prel) and no options to change it. I then hit Save. When I open Adobe later and try loading media the files are not listed in the folder I stored them in because .prel is not in the list of supported formats. So I find the file in Explore and click on it and it occasionally opens Adobe and loads. If it doesn't load I get a message "Type of file is not supported or the type of codec is not installed". I check the updates on my program and it said everything was up to date. I use the same routine but am getting different results. I'm using Windows 10.

Moved from the Photoshop forum to the Premiere Elements forum.