In the settings Windows has the option "power supply". Its importance can be seen in the "control Panel". By default, the hard disks off after 20 minutes of inactivity – this is done to optimize power consumption. In the tab "power Schemes" you can if you want to put the value "Never" for the option "turn Off hard disks".
The optimal mode of operation in which the hard disk directly accesses memory, called DMA (Direct Memory Access Direct memory access"). In PIO mode (Programmed Input/Output) memory access peripheral devices controlled by the processor. In this case, the Winchester is much slower and may disconnect.
In "device Manager" expand "IDE ATA/ATAPI controllers". Right-click on the channel to which you connected the problem hard disk. Choose "Properties" from the drop down menu and go to the tab "advanced settings". Set the value of the parameter "transfer Mode" is "DMA if possible".
Winchester may be switched off due to power problems. Perhaps your power supply produces low voltage. Try to replace it by another with higher performance.
Inspect the motherboard – the reason for disconnecting the hard drives may become swollen or leaking capacitors.
If during the appeal to the hard drive on sudden loss of power, the heads do not have time correctly to be positioned at the beginning of the tracks. Because of this there is damage to the disc surface. If there are a lot of bad sectors, the hard disk during operation spontaneously turned on.
Right-click on the icon of the hard drive and choose in the drop-down menu "Properties". In the tab "Tools" click on "validate" and check the boxes for the items "Automatically fix errors" and "scan for and attempt recovery bad sectors". To get started, click "Start", then "Yes". After reboot the system will start checking the hard drive.
Perhaps Winchester is switched off due to overheating. Install Everest on your computer and check the hard drive temperature. If it exceeds 50 degrees, increase forced cooling, for example, put additional fans.
Certain viruses can disable the winchesters. Scan your computer with reliable anti-virus program, such as Dr. Web CureIt! Before scanning, be sure to disconnect installed on the computer antivirus program.