Your 'printer' is actually several different devices (printer, scanner, etc) in one box and your computer sees them all entirely separately, as each component has its own driver. If the printer part is working, but the scanner isn't recognised, then your computer clearly can't find the driver for the scanner. So you need to reinstall it. You can either do that from the disc which came with the printer/scanner or, if you tell us the model, I'll give you the link to download it.