First, (assuming you have Windows XP) you want to temporarily remove any imaging devices from any USB ports on the back of the computer (i.e., any combination of printer, scanner, copier, fax machines).
Then go to Start, then go to Run, then type in "services.msc" (without the quotation marks). Look for 3 things; Canon Camera Access Library 8, SSDP Discovery Services, and Windows Image Acquisition (WIA). Make sure they all read "Started" under the Status column and "Automatic" under the Startup Type column. If they aren't started & automatic, double-click the service. Under the General tab, change the startup type to automatic and click the start button to start the service. After that is done, you can close down the Local Services window.
Now try & connect the camera to one of the USB ports in the back of the computer. If you get the "Found New Hardware" window and the Canon Camera Window pops up asking you to select a program, choose Camera Window. It will walk you through the rest.
If it does not give you the Camera Window a few seconds after you plug in the camera, just go to Start, All Programs, Accessories, Scanner & Camera Wizard. That should walk you through the rest.
Hope that helps!