Please refer to the guide Connecting Camera to Computer for further information. Also make sure that the proper software is installed to your computer. This software should be on a CD-ROM which comes with the camera. If you do not have the CD-ROM the software can be downloaded from Canon Software and Drivers.
It is possible that something as small as a grain of sand is stopping the lens from closing properly. Gently wiping the lens in a circular motion with a lens cleaning cloth may resolve this problem. If the problem is not resolved please try the steps in the Camera Lens Error guide.
The camera is not turning on because of a few possible issues. The battery is dysfunctional, misplaced, or you have not pressed down on the power button forcefully enough to turn it on. The guide for the battery can be found here: Charging the Battery and Battery Removal.