TIG's suggestion DOES work !!!
File.identical?("C:/Program Files/Google/Google SketchUp 8/Plugins/testfile.rb", "C:/PROGRA~1/Google/GOOGLE~3/Plugins/testfile.rb")
true
Then, stripping off the filename and testing dir against dir:
File.identical?("C:/Program Files/Google/Google SketchUp 8/Plugins", "C:/PROGRA~1/Google/GOOGLE~3/Plugins")
true
But it's still stupid, that the installer writes 32 bit quoted pathname, and the app overwrites it each time it starts up with a 16bit pathname.
If I start SU7, i wonder if it will overwrite the registry key. Bet it will...