I cannot rename the project using TMG because the file will not open in that program. I tried that unsuccessfully. I also tried manually renaming all of the related files in the source file folder but that did not work either. I still get a message staying that the file/s do not appear to by valid PJC file/s. I think that the file may have become corrupted somehow. I may have to re-enter all of the data into a new project file and start over. Fortunately I will have lost only a few hours of work. However, it concerns me that this might happen again. I wouldn't want to enter all of my genealogy data into a project and then find it cannot be accessed.