Since Office 2007 (and Vista), TWAIN has been kicked out in favour of WIA. As a result, it is no longer possible to use your favourite and robust TWAIN based scanner with Office 2007.
Most scanners come with the necessary software, and thus, you can circumvent the issue by using their software. However, there are various scanners - notably, office network scanners, like those on copiers, do not have such a tool. They have their driver's internal system which is callable in other software (like Office-applications). In the event that the driver is only supporting TWAIN interface for image acquisition, they do not show up in Vista's scanner list, and therefore, they cannot be used by Office 20  ...