Hard disk not getting detected.Seagate 80 GB - Seagate Computers & Internet

If your hard drive is an IDE type, the data cable that connects it to the motherboard will be a flat (usually gray colored) cable that has three 40 pin female connectors on it. If it is an 18" cable, the 2 connectors that go to IDE devices (hard drive or CD-ROM) will be spaced about 6" apart at one end of the cable and the connector that connects to the motherboard will be at the far end of the cable. Also, the cable will have a red stripe along one side of it. The stripe is an indicator of where pin # 1 is on the cable.
Since the IDE cable connects to two devices, there has to be a way for the motherboard controller to know what is connected to each connector. This is accomplished by small straps called jumpers on the rear of the IDE devices. The jumper choices are Cable Select (CS), Master (MA), and Slave (SL).
If your hard drive is strapped as master you must connect it to the connector at the end of the cable. ( If there is a second device on the cable it must be strapped as slave.)
If your hard drive is strapped as Cable Select it is usually connected to the end of the cable but any device on the 2nd connector must also be strapped as Cable Select.
Verify that the hard drive is strapped properly and then be sure it is connected to the drive with the red stripe side closest to the hard drive 4 pin power connector.
At the motherboard end, be sure the cable is connected with the red stripe side adjacent to pin 1. A "!" is usually marked on the motherboard next to the pin 1 of the IDE socket.
Verify that a 4 pin power connector is plugged into the connector on your hard drive and be sure it is fully inserted. .
If you have a SATA drive, the connections are easier. Verify that one end of a SATA data cable is connected to your hard drive and the other to the first available SATA connector on your motherboard.. Then verify that a SATA power cable is connected to the power receptacle on your hard drive.
When you are sure your connections are correct, plug in and as you turn on your PC, hold down the delete key to enter BIOS setup. (On some machines it's the F!, F2 or F10 key).
Once in BIOS setup, press the Enter key to select the first display screen, ususally titled "Standard CMOS Features". Your Hard Drive should be listed under IDE or Sata devices. If it is, follow the on-screen instructions to get to the Boot Menu. If this hard drive is the device that you want to load your operating system from, be sure it is listed as one of the boot choices.
If the CMOS Setup screen does not see your hard drive, then you need to have the drive and your PC tested by a PC technician to determine what the problem is.
I hope this information is of assistance to you. If you have any qustions please contact me..
Yacacotech

One bad lead can cause a computer to fail to detect a hard drive continue on a cycle or to shutdown

Test all leads that attach to your hard drive including electrical extensions,IDE,SATA and

the leads from your motherboard to your hard drive make sure they have a secure connection and are not faulty or just replace them there probably old and faulty
problems
make sure all leads that are attached to your drives dvd\cd 3 1/2 inch floppy have secure connections and are not faulty or just replace them they are probably old and faulty ?
hope this helps