To answer your question directly, put r in front of the string.
final= path + r'\xulrunner.exe '+ path + r'\application.ini'More on Python's site here
Both string and bytes literals may optionally be prefixed with a letter 'r' or 'R'; such strings are called raw strings and treat backslashes as literal characters
But a better solution would be os.path.join:
final = os.path.join(path, 'xulrunner.exe') +''+ \ os.path.join(path, 'application.ini')(the backslash there is escaping a newline, but you could put the whole thing on one line if you want)
I will mention that you can use forward slashes in file paths, and Python will automatically convert them to the correct separator (backslash on Windows) as necessary. So
final = path +'/xulrunner.exe '+ path +'/application.ini'should work. But it's still preferable to use os.path.join because that makes it clear what you're trying to do.