If you look around in the registry you should find HKEY_CURRENT_USER\SOFTWARE\Scirra\Construct2\NodeWebkitPath, which is the first path it checks.
If it can't find NW.js at that path, it checks a hard-coded fallback list of the following paths:
C:\Program Files\NWjsForC2\
C:\Program Files (x86)\NWjsForC2\
C:\Program Files\NodeWebkitForC2\
C:\Program Files (x86)\NodeWebkitForC2\</p>