|You must get the computer's bios to recognize the hard drive. |
Make sure all drive connections are set to Auto detect drives by the method Auto or LBA, or similar, in the bios Setup. If that is wrong, change that, Save bios settings.
The hard drive data cable should usually be connected to the Primary IDE header on the mboard, and if the optical drive is IDE, it should usually be connected to the Secondary IDE header.
Usually when the bios isn't recognizing a hard drive, either the jumper is set wrong for the situation, or you have a problem with the (IDE in this case) data cable.
Make sure you have the jumper (or no jumper) setting set correctly. Sometimes the label with that info that's on the top of the drive is upside down in relation to the back of the drive. If the label shows where the power connector is, go by that relative to the jumper. If in doubt, you may need to look up the jumper info on the web.
If there is another drive on the same data cable, you may need to change the jumper setting for the hard drive, or the other drive.
Check your IDE data cable.
See response 4: