This means that the system has lost their .reg file program association. You can restore this in the
1. open Registry Healer backup folder in explorer;
2. hold Shiftkey on your keyboard and right mouse click on a .reg file to pop-up menu;
3. select the "Open with.." command from the menu;
3. click "Browse.." button (or "Other.." button in Windows® XP) and select "C:\Windows\regedit.exe" file ("C:\Windows\" is a path where your system is installed). Be sure that the box "Always use this program for such files" is checked.
Next time you click on a .reg file it will be imported into the registry with help of regedit.exe that is default system handler for .reg files.