If you manually installed a custom map and you then removed the map, chances are RWR won't launch anymore ending with a crash-like dialog with something about Ogre, exception and terrain5 heightmap not found. This happens because your settings are still pointing to the last map you played, which no longer exists, and RWR halts when loading the map.
If you're a victim of this case, you know that even re-installing the game won't help. That's right, it doesn't yet, but it will one day in the future.
For now, here's your answer:
http://modulaatio.com/runningwithrifles/rwr_clean.exe* Download rwr_clean.exe anywhere, on your desktop for example
* Run it
The tool locates RWR settings.xml on your system and deletes the file. You'll lose your key config and other settings, but now you can start the game properly again.
You can do it manually too, by accessing "C:\ProgramData\Running with rifles\" in Windows 7 and Vista , or "C:\Documents and Settings\All Users\Running with rifles\" or "C:\Document and Settings\All Users\Application Data\Running with rifles\" in Windows XP. You might not get to the location by just navigating towards it in Windows Explorer as the folder is usually hidden by default in Windows. Use the Windows Explorer address bar or Start Menu -> Run and type the location there to get there. Either delete the file, or open it, and edit map_resource_location field to point to a valid location. Done!