Well, you haven't given us a lot of information to work with. But here's one possibility, based on a past thread.
This is a Targa file, an image file that I think might be included on one of the Movie Menus or a Title template.
Try swapping in a different Movie Menu or Title template and see if that message appears next time you reload the project.
It is not going to do you much good even if you find a .tga file. Premiere Elements 11 and 12 do not support .tga files.
Premiere Elements 4 through 10 do.
Let us back up a little. You say that you cannot open a project (project.prel file) that you created? Do you remember what you included in that project in the way of Instant Movie and Title Template?
With that information I think that we can clear up the mystery of the "Where is the file....tropical_7.tga."
The file tropical_7.tga was reported to exist
Program Files (x86)\Adobe\Adobe Premiere Pro CS4\Presets\Textures\Tropical_7.tga.
Some overzealous designer may have written that in a Title template or Instant Movie but never supplied the file because it was tga was not supported. Just guessing. But, your information on what went into your project should help us figure this out.
Add On...The following is my blog post on a recent "glitch" in the Instant Movie Outdoor Adventure.
I thought that your issue might be a simple Adobe Instant Movie or Title Templates glitch.
But, I just came across the following on tropical_7.tga
I am still going through the article trying to determine what it is all about.