I'm not to sure on this one, but as no one else is around to help at the moment, I'll try.
If you have a start-up floppy disk, use this to arrive at the a:/ prompt, and type the word, FORMAT C:
Notice the space between the backslash, and C:
Then just follow the on-screen prompts and try to set the drive as one partition, see if this enables the BIOS to find your drive. J.