Ditto what Augi said. The software is just another layer of silliness for the most part. Just open that bad boy up from My Computer and pull the pics from the DCIM folder.
Hmmm, secondarily, do other plug and play devices work? If your mouse is USB and you can unplug and plug it back in and have Windows recognize it, your PnP is working fine. Generally, Plug and Play, as a system, can't really break, and it certainly cannot selectively break (ie - using the test above). If a driver goes out, most modern USB devices would cease to exist on your PC as they are pretty much all PnP. Could be a bad cable (PWR+GND will trip detection on some devices, but bad DATA will not allow an actual connection).
Okay, I reread your last post. If the computer sees the camera (does it recognize it including model?) then PnP is not the problem. Plug and Play is a transparent background service in Windows that offers information about connected devices to other applications (and to Windows itself).
- If the Camera shows up in Device Manager as "Canon Model xxxx" then PnP is working as intended.
- If it shows up as "Unknown Device" then there is a driver problem (driver was corrupted at some point, try system restore from recent backup?).
- If it shows up as a gibberish device, then there is a firemware issue with the camera.
- If the camera does NOT show up, then there is either a camera hardware problem, a cable issue or an actual PnP issue with Windows (try an XP reinstall).
Good luck!