There are two forms of failure in a hard drive, logical and physical.
1. Logical failures are usually a result of file-system corruption. Typical symptoms involve the computer being stuck in a loop where it boots, starts to go into Windows, and then reboots itself. You may also get the "Blue Screen of Death". Additionally, you might also have a logical failure due to a virus, accidental deletion of key files or registry components, and in some cases even electro-static discharge. In most cases where a logical failure has occurred, the drive is still recognised by the system BIOS, but it will not boot. Your data should still be intact on the drive, even though it may appear to be inaccessible.
2. Physical failures can result from a wide variety of causes.If the system BIOS does not detect the presence of the hard drive, then chances are a physical failure has occurred.If the system BIOS does not detect the presence of the hard drive, then chances are a physical failure has occurred.
If your drive is making any unusual noises.
SHUT DOWN YOUR COMPUTER AND DO NOT RESTART IT!!!!!
Another physical issue that sometimes rears its ugly head is an electronic failure. If you look at a hard drive you will notice a circuit board on the bottom. This board is basically the brains of the drive, and it is where the computer interfaces to the hard drive. An electrical failure can occur unexpectedly at any time. Even brand new hard drives are not totally immune to having electrical failures. Sometimes it's just a faulty component, sometimes it's improper installation (i.e. electro-static discharge, grounding out the board, damaging circuitry during installation). It's important to also keep your system clean and well ventilated, since excessive heat can damage the electrical components on the drive. If you have a system that is in a somewhat contained area, you may look at adding an additional 80mm fan to cool the internal components of the system, especially the hard drive. No other component of a computer works as much as the hard drive, and therefore it is vitally important not to overlook it when cooling issues arise.
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