My computer cannot detect my camera - Canon PowerShot A520 Digital Camera

Have you loaded the appropriate software? If not: http://www.usa.canon.com/consumer/controller?act=ModelInfoAct&tabact=DownloadDetailTabAct&fcategoryid=320&modelid=11125

If you already have and have connected your camera to the computer but still does not detect it, try uninstalling the program completely and reinstalling the software.

I just experienced this problem and went round in circles for a few hours before stumbling on the solution. My camera, a Sony Cybershot, has 4 USB Connect modes in the Setup menu: PictBridge, PTP, Mass Storage, and Auto. The only mode that would work to bring up the Camera Wizard screen on an XP computer was PTP. Once I changed the setting from Auto to PTP, the camera was recognized and able to connect to the computer. Somehow this setting had got changed to Auto or Mass Storage and that evidently causes a problem such that XP does not recognize the camera.