You could just re-install Lightroom 5 and use it.
LR 5 is still on your system unless you specifically removed it. It is in the either the Applications folder (Mac) or C:\Program Files\Adobe (Windows).
Just find the Lightroom.exe (Windows) or Lightroom.app (Mac) file and double click on it. You can also make a Shortcut or Alias (Windows or Mac respectively) to that .exe/.app file on the desktop or Start menu or Dock.
To stop LR from crashing turn off the Use Graphics Processor option in the LR Preferences.