The files have not been affected, it is just the file association what was modified.
-Right-click on any .FMX file and choose “Open with…” from the PopUp Menu.
-Select the “Select program from a list” radio button and click “Ok”.
-Look for the Forms Runtime in the programs list. If it is not in the list, press the “Browse…” button and navigate to your Forms “BIN” directory to select the file called “ifrun60.EXE”.
-Make sure the “Always use the selected program to open this kind of file” check box is selected.