problems after restoring from backup

I have a small windows 2000 active directory domain at home for learning puposes.I changed hard drives on my workstation and before i did this i backed up my workstation to the server including all files and system state data.After i reinstalled win2000 pro I restored it from backup.Now here is my problem,I had to reinstall the drivers for my modem,sound card ,video card,and printer.Also about half of my programs think im a new user and want me to register them or buy keys.Why is this