As you know, the hard drive in any computer is one of the most important components. But sometimes it can cause a lot of problems. One of the most common is the situation when the hard drive disappears, and it becomes impossible to work or even load the operating system with the programs installed in it. What is the reason for this phenomenon and how to eliminate possible malfunctions, then it is proposed to figure it out.

Hard drive intermittently disappears: connection check
In general, the main reasons that the system suddenly stops detecting a hard drive are called hardware problems, not software problems (although this can also be found).
Usually, most experts recommend immediately checking the special cable through which the hard drive connects to the motherboard, and the tightness of the hard cable contactsdisk on the device itself. Along the way, note that the cable itself should not have a bend of more than ninety degrees, that is, it is strictly forbidden to fold it into several layers. This is understandable, because contacts can simply break. If, when connecting the hard drive cable to another device, its performance is fully ensured, this means in most cases that the reason for this phenomenon lies in the hard drive itself. But this is not always the case.
Problems with power supply
To no lesser extent, the power supply unit, which simply does not have enough power to provide all the "iron" components of the computer with the required voltage, can also have a negative impact on the operation of the hard drive. This is especially true when the computer configuration is assembled by hand. To get started, read the technical documentation of the device itself, check the supplied current with a tester, and if necessary, replace the entire unit.
Note: sometimes the appearance of constant spontaneous reboots of the system can also indicate an insufficient power supply.
Overheating
But let's assume that it's not the above reasons. Where did the hard drive go when you turned on the computer or in a running system, because everything seemed to be working fine before the problem appeared?

It may very well be that the problem is that the hard drive is constantly overheating. You can find out if this is so with the help of special utilities that display the characteristics of all available devices. For example, you can use the HWMonitor program. After determining the temperature parameters of the hard drive, it will become clear whether the problem is related to overheating. For most hard drives, 30 degrees Celsius is considered normal, and the maximum withstand is no higher than 45 degrees. If the limit is exceeded, most likely, you will have to deal with either the cooling system or the device itself.
Hard drive failures and errors
Quite often you can meet situations when the computer worked, but at one "perfect" moment the hard drive disappeared for no apparent reason. The computer does not start loading, or this happened directly when working with it, in this case it is not so important. The reason for this is usually called a breakdown of the device. This can be found, for example, when the hard drive, as they say, began to crumble. Programmatically, as a rule, it is quite difficult to determine the true cause. But first, you can try to connect the hard drive to another computer. If the hard drive is detected, then the problem is with another component (usually the motherboard). If it is not visible, the easiest solution is to buy a new one.

But if the hard drive disappeared for a while, and then was determined again, you can at least check it for bad sectors via the command line, using the chkdsk /x/f/r command for this (when the console starts from removable media, between the main command and the attributes, you will need to specify the letter of the system partitionwith a colon).
You can restore the hard drive in another way. To do this, you can use the HDD Regenerator application, which supposedly remagnetizes the surface of the hard disk by software.
Why doesn't Windows 10 see my hard drive when waking up from sleep or hibernation?
Despite hardware failures, sometimes you can encounter problems related to the operating system itself and its parameters. Often, according to some experts, the same Windows 10 does not see the hard drive (after a certain period of time) just because the hard drive is disabled in the settings of the current power plan.

In the scheme parameters, in this case, it is necessary to set a prohibition on shutdown. In some cases, you can try to disable fast startup or even deactivate hibernation by running the command powercfg –h off in the command console (at the same time, by the way, the hibernation file will also disappear from the hard disk, which can take up too much space on the system partition).
Troubleshooting system components
But very often the hard drive disappears not even due to the reasons described above. Sometimes this is facilitated by a violation of the integrity of system components. And the fact that the hard drive disappears is only the result of failures in the software part of the operating system.

If the system cannot be booted even using safe mode, you canstart from removable media, then call the command line (Shift + F10), and then run the command to check and restore system objects sfc /scannow. Sometimes, of course, you can use the DISM toolkit, which allows you to check and restore system images, but standard testing is usually enough.
Information recovery
Why the hard drive disappears and how to deal with it, figured it out a bit. It remains to say a few words about the recovery of important data, if the hard drive shows at least some signs of life. In this case, it is recommended, if possible, to copy the necessary files to removable media (rather than to a logical partition, which is also actually on the hard drive).

But for direct data recovery it is better to use the R-Studio program, and not some simple utilities like Recuva. If none of the methods gave the desired effect, and the use of the HDD Regenerator program also turned out to be ineffective, the hard drive will either have to be handed over for repair to a service center or replaced. There's nothing to be done.
Summary of conclusions
As it is already clear, the most frequent are still hardware problems, so first it is better to use methods designed to eliminate them. Software failures can only be the result of breakdowns or incorrect operation of the device, so they should only be used in situations where the initial actions do not reveal problems. If when the hard drive disappears from the field of view of the systemblue screens also appear, you can determine the exact cause of the failure using the BlueScreenView utility.
It remains to be added that the problems associated with changing the file system to RAW format, reassigning partition letters, initializing the device on first connection and virus exposure were not considered here, since all this has only an indirect relation to the main situation.