If this scanner is anything like the two Canon's that I have it is impossible to install directly from a set up file, or by simply unzipping the driver.
You have to first connect the scanner when your PC is switched off, both by the mains cable and the USB cable, and then switch on. Vista should then detect the scanner (if it doesn't and some can play up) repeat this step. When detected choose to install from a specified location. DO NOT CHOOSE TO INSTALL AUTOMATICALLY. In the browse box that appears go to the folder where your unzipped driver is and highlight the .inf file which should be in the root folder of the unzipped files. Ok through the rest and that should be it.
The Scangear Toolbox will probably not work in Vista, and I would not even bother.