I followed the Support link from that link but it doesn't give you the basic drivers.
I can't help thinking I am missing a trick here because I don't remember having this trouble a couple of years ago when I set up the same printer on my other Win 7 machine.
I am currently using the original Hard Drive for the documents etc on it. If I can't resolve this tonight I am going to have to re set up my opld machine just to get these documents printed. That will be a drag!
According to the Microsoft Compatibility Centre the ip3000 is fully compatible so Windows 7 should find the correct driver for it. I would have one more try of uninstalling the "other" printer and try again. Right Click on it and select Uninstall this Device. Either switch the printer off or unplug the USB connection and reboot. Once the PC is up and running switch the printer on (or plug the USB back in again) and let Windows find the printer. See if that works.
If you work your way through the Canon support website for the ip3000 for English and Windows 7 software I found the bottom one was "Canon Inkjet Printer Driver Add-On Module File version: 1.10" which adds functions for Win 7 and Vista
I have MS Office 2010 installed and it was registering One Stop 2010 as the default printer. As soon as I uninstalled it the ip3000 moved from 'unspecified devices' to the main section and automatically installed the drivers.
It might not be the answer, but I had a similar problem with an HP printer. Contacting HP support, they suggested that I used another driver from another printer in their range. It worked, problem resolved.
So perhaps contacting the printer manufacturer might resolve the issue?.