canon a540 connection error via usb

Instead of installing the software first I decided to connect the camera since Windows XP supports plug and play. That did not work and Windows said it was unable to install the software. Then I followed the steps in the manual which told me to install the software, then connect the camera but no message popped up. Then when I go to add hardware it displays an error message saying a previous version of the Canon camera is already in memory. Error code thirty eight was displayed w/ this message. I installed the camera on another Windows xp pro computer, with the software installed first and it worked fine. Canon states that I can plug this camera into a Windows XP computer w/o the need for software so I don't why it didn't work the first time. There has to be a way to start completely over. I've uninstalled the software and that hasn't helped. There is an option to uninstall the driver but that only displays when the camera is on and connected to the computer. Would uninstalling the driver while the camera is on cause any problems?

Ricky