First off bogdantalpa hasn't specified which flavor of 7 he is running there. Even with the 32bit 7 the support site shows a lack of any Vista updates showing what is available was written primary for 2000, XP, and the older Legacy versions of Windows.
Due to rapid change of model lines and problems with older hardwares, devices with each new version of Windows seen you are likely better off considering going with a newer model that does see Vista, 7 updates right off. The alternative would be finding a different very similar model that does see updates or trying out some generic drivers
in the hopes that one of those will work.
Someone seems to have solved the same problem but for Vista however. Review the thread seen at the driverguide site. DRIVER NEEDED: Canon CanoScan N650U (Windows Vista) [USB] - DriverGuide Support Forums
Note the thread was from 2008.
At least at the first support page there was some driver
sets available while the European site however shows nothing at all. Canon Software Centre - Search results