Canon Pixma MP160 Scanner on 1.83GHz Intel Imac running OSX 10.4.9

Hi, I've been using the Canon MP160 for ages now for printing with my Intel Imac running OSX 10.4.9 & connected wirelessly thru my Apple Airport Express. The computer is downstairs & the printer is upstairs. There's never been a problem with the Airport connection (the printer is connected via a USB cable to the Airport itself) & the printer works perfectly. The problem is the scanning side of things - I just can't get it to work!! I found a little read me file with the originl install files which gave me instrucions specific to Intel macs to open Image Capture (from the Aplications menu), select Browse Devices, select Canon MP160 from the TWAIN devices menu, select Use TWAIN software box & click OK, close Image Capture & then open it again & select MP160 from the devices menu - I followed all this until the last bit, but Canon MP160 was not in the devices menu & Image Capture resolutely failed to recognise that any scanner was connected!! I have downloaded the scanner driver from the Canon website & reinstalled that, still to no avail & basically I'm out of answers!!!! Help!!