From the information you have provided the most obvious conclusion is that something is wrong with the motherboard. We hope that's not the case. Other things are floppy drive itself, the CD-ROM drive and a power supply. And possibly, even your graphics card, if his computer as a separate graphics card.
When this sort of thing happens , here are procedures technician will use on the most personal computers. First eliminate floppy drive and the CD-ROM drive by removing them completely from the system, removing both the power and data cables. Under those conditions BIOS now should recognize the hard right even if you don't have jumpers set properly. Still, make sure the jumpers are set correctly.
The other thing to check is the cable going from the hard drive to the motherboard. The cables normally don't go bad by themselves. Unless you've been pulling on the lately and you broke something.
Sorry to be a bearer of bad news, but if you can't get it to find the hard disk drive, you're in a tight spot.
Oh, check the CMOS battery. Got right time and date? default settings?
