Go to the following page: http://www.usa.canon.com/cusa/support/consumer/scanners/canoscan_series/canoscan_lide_20#Overview and select Windows 7 (Not 64 bit, there is no 64 bit driver available.) as the operating system. Then click on drivers and follow the prompts to download the driver. Or, as an alternative if you haven't yet tried it, you can go into Control Panel and open Device manager. In device manager there should be a device with a question mark or exclamation point next to it. Right click on update drivers and follow the prompts to update automatically.
Is the device connected? Do you see the device in device manager under ANY of the categories? Under scanners? Apparently Canon does not support this device for 64 bit operating systems, they say it's too unstable according to tons of forum threads. The only other option you have is to buy Vuescan from this third party company which they have indicated WILL work with your device under Windows 7 64 bit. It sucks to have to buy something that should be free but it's all I could find and there are other Tom's threads on this and that's what they had to do. You can find the page here: http://www.hamrick.com/vuescan/canon_lide_20.html