I would try resetting the preferences first:
Restore default preferences
Preference settings control how Photoshop Elements Editor displays images, cursors, and transparencies, saves files, uses plug‑ins and scratch disks, and so on. If the application exhibits unexpected behavior, the preferences file could be damaged. You can restore all preferences to their defaults.
Note: Deleting the preferences file is an action that cannot be undone.
Do one of the following:
- Press and hold Alt+Control+Shift (Mac: Option+Command+Shift) immediately after Photoshop Elements begins launching. Click Yes to delete the Adobe Photoshop Elements settings file.
- Go to Edit > Preferences (Mac: Photoshop Elements > Preferences > General), click the Reset Preferences on next launch button, and then click OK. When you restart Adobe Photoshop Elements, all preferences are reset to default settings.
If that doesn't work, try uninstalling and reinstalling.
Rather than opening project files from an external drive, it would be better to copy the project file to your internal hard drive and open that file.
Do you have backup project files?
Thank you, Peru Bob for your answer. Adobe Photoshop seems to work properly and doesn't need to reset preferences settings or I am wrong? I have trouble with Premier Elements 15 damaged project files and opening that particular program. Unfortunately I did not back up project files from Premier 15. I think that I should put in my question one sentence more. I use Bitdefender Internet Security 2016.
Thank you again! I have tried to contact Adobe Customer Service. Ajay Sharma successfully helped me to resolve the problem on June 12 2017 by using remote control of my PC. Files were retrieved and PRE 15 now opens without any difficulties.
Glad you've got it working.