I have an Canon CanoScan N650U scanner that I use a few times a year. Canon never released Vista drivers for this scanner, using the instructions below made the scanner work on Windows 7 for me:

1. Download the XP drivers from Canon’s website
2. Install the drivers
3. The driver didn’t install, but unzipped to C:/Temp/CanoScanCSUv571a
4. Go to C:/Temp/CanoScanCSUv571a and uncompress CanoScanCSUv571a.exe
5. Plug in your scanner
6. Go to your device manager.
7. Click on Add a Device and select the scanner
8. Right click to update driver information
9. Select browse my computer for driver software
10. Type in: C:\Temp\CanoScanCSUv571a
11. Click next and my scanner worked

Update: In the comments Paul wrote, “I used the WIA drivers, which I found here: http://www.normalgeeks.com/Canoscan_WIA.zip”  I haven’t tried it, but’s worth checking out.