How can I re-install SBS 4.5-NT4 server

How can I reinstall Small Business Server 4.5 OS or just components like exchange, IIS, etc? I have some file corruption problems and some services won’t work properly. How can I re-install the operating system without destroying my data. I know exactly how to do this with windows 9.x any version, but I am unfamiliar with NT. My CD is not an upgrade so I believe it only wants a fresh install creating a new partition or using an old one but overwriting all data. Any sugestions, please help.