Format c: on Deskpro 2000 to load win98

I have a Compaq Deskpro 2000; I loaded the diagnostics and f10 function on disk from diskettes after removing all partitions. On subsequent running of fdisk and format C: to get ready to load windows 98, I get the following
error when running format c: “Format not supported on Drive c: Format terminated”
Why do I get this and what do I do to get around it and on with the load?