hd detection?

I’ve got the cmos set to recognize the 4.3 gig hd. And it does,it shows it to be the master on the primary ide controller. But, when I boot up the system, it won’t detect the hd. Just the floppy drive. It shows “disk I/O error replace the disk, and then press any key. It’s set in the properties to boot from the A drive, then the C drive. If I put a bootable floppy in and boot up with cd rom drivers. It recognizes the cd rom drive as C drive. Any ideas here?