Corrupted desktop database file. The Finder keeps a database that it uses to organize the files in your system. It is a good habit to periodically rebuild this database so that the Finder can reorganize itself to include new files in the database. It is not uncommon for this file to become corrupted in some way, causing all sorts of inconsistent relationships between files and their supportive applications. A message will appear asking you to confirm the process.
Corrupted settings file.
This file stores all the preferences that you set from within the program. However, you will lose any preferences that you've set within the program. Incompatible plug-in file. However, not all plug-ins will work. Most notably, most of the plug-ins that ship with the Photoshop package itself are designed by Adobe specifically to run only in Photoshop, so they will not work other programs.