http://www.usa.canon.com/cusa/support/consumer/scanners/canoscan_series/canoscan_lide_20#DriversAndSoftware
Windows 7 drivers here ^ Select windows then choose Windows 7
And it says there is no driver. Canon don't support win7 64 for those scanners, claim it is too unstable, i.e. they want you to buy another scanner.
You can use: http://www.hamrick.com/ it does work, or it did on my lide 20 with win7 64.