You don't mention 32 or 64 bit windows.
Hopefully you have 32-bit, in which case you can download and install the Vista driver from here:
http://www.canon.co.uk/support/consumer_products/products/scanners/canoscan_series/canoscan_n1240u.aspx?type=drivers&language=&os=WINDOWS%2010%20(64-bit)
If you have 64-bit, it's time to replace the device as Canon has not made 64-bit drivers.