Windows 98 installed on D: drive

I have a client that has Windows installed on the D: drive. I am installing a new 40GB hard drive in their system and would like to get this system back to a standard Window 98 install. I do not want to re-install all the software, if I can avoid it. The system boots from the C: drive and Windows 98 loads from the D: drive. Can someone give me some solid advice on how to get this system back to a standard Windows 98 Configuration?

Thanks for the help in advance

John B