I have reset the program to default but now can no longer find the project that I had been developing. I should be grateful for any advice as to how to retrieve it.
By default the project files should be in Documents\Magix\Projects.
If you had changed this setting previously in the Program Settings, Folder tab or saved the projects elsewhere then I would suggest to use Windows File Explorer to search for the projects - enter the search term as: *.MVP if you have only one hard drive (C:) in your computer start the search from there.
If you have more than one hard drive or used an external hard drive then try searchin those..
If you saved the project files to your desktop, please be aware that this is not a protected folder and can be reset by Windows or a Windows upgrade resulting in loss of the files and other documents saved on the desktop - the Documents folder is a protected folder.