What computer operating system is your Premiere Elements 10 and 7 running on? Background information.
1. You cannot open a Premiere Elements 10 Windows project file (project.prel) in an earlier version of Premiere Elements Windows (in your case, Premiere Elements 7).That is it. No workaround. Unless, do you want to consider exporting the Premiere Elements 10 Timeline to a file saved to the computer hard
drive and then importing that file into Premiere Elements 7 as source media?
Depending on the circumstances, there is a good likelihood of opening a project created in an earlier version in a later one (but no guarantees). But,
after you edit the earlier project in the later one, you cannot go back and edit the later-version-edited one in the earlier version. The generalized recommendation is to work on and finish the project in the version in which it was created.
2. For future reference, you cannot open a Premiere Elements 10 Windows project file (project.prel) in Mac Premiere Elements 10 and vice
Please let us know if you have any questions about the above or need clarification on anything written.