Machine will not boot up..replace disk??

When trying to boot up getting a message…
“Invalid system disk. Rreplace the disk, and press any key”

There is no floppy in the machine.
We’ve shut off, and tried again, still same message.
Tried using windows startup disk, ran scandisk.. repaired some errors…still not any difference.

when attempting to open a c: promt through the startup disk.. get this error
“cdr101:not ready reading drive H
abort, retry, fail?”

any help would be appreciated…