I have recently had a new laptop and want to install this scanner but have lost the disc. I have been informed by a salesperson in Pc world that I won't be able to get another one. Can anyone tell me in PLAIN ENGLISH how to install without a disc Many Thanks

This site has the drivers for your scanner:

Downloads - Diamond 1200 plus USB flatbed scanner - platform_scannerdiamond1200plus - Accessories

The bad news is that drivers are only available for XP, if it's a new laptop with Windows Vista, they probably will not work. So its tinme to get a new scanner.