PaulS:
But it come along when I download the arduino 1.0.5 file. Why you would say that it is user-downloaded library file ?
Because the install path for the Arduino IDE and related code usually has the version number in the path. The sketch directory usually does not. Therefore, when I see a path without a version number, I assume that it is a sketch directory, and that is where user-downloaded libraries go. There are good reasons for following conventions.
So what should I do now ? Redownload the IDE ?
Thank you