Computer hard drive trace elimination

Computer Store News Top Ten Tips for Rescuing Hard Drives

Each user's hard drive has a lot of useful data stored in it, and the hard drive is a troublesome part. In order to effectively save the data in the hard disk, in addition to effectively saving the data in the hard disk, backup work, but also learn how to save the hard disk in the event of a hard disk failure, or extract useful data to minimize the loss.

1, the system does not recognize the hard disk

This type of fault is more common, that is, the hard disk can not be started, can not enter the C drive from the A drive, can not be found using the automatic monitoring function in CMOS The existence of the hard disk. Most of these faults occur on the connection cable or the IDE port. The failure rate of the hard disk itself is very small. The replacement test can be performed by re-plugging the hard disk cable or changing the IDE port and cable. The fault can be quickly found. If the newly connected hard disk does not recognize, there is a common reason for the master-slave line on the hard disk. If the hard disk is connected to the IDE's main disk, the hard disk must be the main disk. The jumper error cannot be detected. hard disk.

2, CMOS caused by the fault CMOS's correct or not directly affect the normal use of the hard disk, here mainly refers to the type of hard disk. Fortunately, today's machines support the "IDE auto detect" function, which automatically detects the type of hard disk. After connecting a new hard disk or replacing a new hard disk, you must re-set the type with this function. Of course, there are now types of motherboards that automatically recognize the type of hard drive. When the hard disk type is wrong, sometimes the system cannot be started, and sometimes it can be started, but a read/write error occurs. For example, if the hard disk type in CMOS is smaller than the actual hard disk capacity, the sectors behind the hard disk will not be read or written. If it is in a multi-partition state, individual partitions will be lost. There is also an important cause of failure. Since the current IDE supports logical parameter types, the hard disk can use Normal, LBA, Large, and so on. If the data is installed in the normal mode and changed to other modes in CMOS, the hard disk read/write error will occur because the physical geological mapping relationship has changed and the original correct hard disk position cannot be read. . 3, the boot failure caused by the main boot program The main boot sector of the hard disk is the most sensitive part of the hard disk, the main boot program is part of it, this program is mainly used to detect the correctness of the hard disk partition, and determine The active partition is responsible for handing over the bootstrapping to the DOS or other operating system of the active partition. Damage to this program will not be able to boot from the hard disk, but the hard disk can be read and written after the soft zone or zone. The method to fix this fault is relatively simple. It is most convenient to use the high-version DOS fdisk. When running with the parameter /mbr, the main boot program of the hard disk will be directly replaced (rewritten). In fact, the main boot sector of the hard disk is created by this program, fdisk. The exe contains a complete hard disk master bootloader. Although the DOS version is constantly updated, the hard drive's main boot program has not changed from DOS 3. x has DOS for winDOS 95, so just find a DOS boot disk to boot the system and run this program to fix it. In addition, other tools such as kv300 also have this feature. 4, partition table error boot failure failure Partition table error is a serious error of the hard disk, the degree of different errors will cause different losses. If there is no active partition flag, the computer will not start. However, after booting the system from the soft zone or the optical zone, the hard disk can be read and written, and the active partition can be reset by fdisk. If a partition type is wrong, it can cause the loss of a certain partition. The fourth byte of the partition table is the partition type value. The normal bootable base DOS partition value greater than 32 mb is 06, and the extended DOS partition value is 05. If you change the basic DOS partition type to 05, you will not be able to boot the system and you will not be able to read or write data. If you change 06 to a type that DOS does not recognize, such as efh, DOS thinks that changing the partition is not a DOS partition, and certainly cannot read or write. Many people use this type of value to implement the encryption technology of a single partition, and restore the original correct type value to restore the partition to normal. There is additional data in the partition table to record the start or end address of the partition. The corruption of these data will cause confusion or loss of the partition. Generally, manual recovery cannot be performed. The only way is to rewrite the data with the backup partition table data, or obtain the partition table from other hard disks of the same type and with the same partition status. Data, otherwise it will cause other data to be permanently lost. When the main boot sector is operated, tool software such as nu can be used, which is very convenient to operate, and can directly read, write or edit the main boot sector of the hard disk. Of course, debug can also be used, but the operation is cumbersome and has certain risks. 5, the hard disk failure caused by the partition valid flag error There is still an important part in the main boot sector of the hard disk, that is, its last two bytes: 55aah, this word is a valid flag of the sector. When booting from a hard disk, floppy disk or optical zone, these two bytes will be detected. If it exists, a hard disk is considered to exist, otherwise the hard disk will not be recognized. When this flag is booted from the hard disk, it will be transferred to rom basic or prompted to be placed in a floppy disk. It cannot be transferred to the hard disk when booting from a floppy disk. Here you can use the encryption technology for the entire hard disk. The debug method can be used for recovery processing. In addition, the DOS boot sector still has such a flag. When the DOS boot sector has no boot flag, the system boot will be displayed as: "missing operating system". The repair method can be used to repair the main boot sector, but the address is different, the more convenient method is to use the following DOS system common repair method. 6, DOS boot system caused by boot failure DOS boot system is mainly composed of DOS boot sector and DOS system files. The system files mainly include iosys, msdos.sys, command.com, where command.com is a DOS shell file, which can be replaced by other similar files, but by default it is a necessary file for DOS startup. In the DOS system that Windows 95 carries, msdos.sys is a text file that is required to start Windows. But you can use this file only when you start DOS. However, when the DOS boot error occurs, the system can be booted from a floppy disk or CD, and then the sys c: transfer system can be used to repair the fault, including the boot sector and system files can be automatically restored to the normal state. 7, read and write failure caused by the fat table fat table records the storage address of the hard disk data, each file has a set of connected fat chain to specify its cluster address. Damage to the fat table means the loss of file content. Fortunately, the DOS system itself provides two fat tables. If the currently used fat table is damaged, the second one can be used for overlay repair. However, because the length of the fat table and the address of the second fat table of different specifications are not fixed, the correct location must be correctly found when repairing. Some tools such as nu have such a repair function, and the use is also Very convenient. This can also be done by using debug, that is, using the m command to move the second fat table to the first table. If the second fat table is also damaged, the hard disk cannot be restored to its original state, but the data of the file is still stored in the data area of ​​the hard disk, and can be repaired by the chkdsk or scandisk command, and finally *. Chk file, this is the sector data of the lost fat chain. If it is a text file, it can extract and merge the complete file. If it is a binary data file, it is difficult to recover the complete file. 8. Boot failure caused by directory table corruption The directory table records the file name and other data of the file on the hard disk. The most important one is the starting cluster number of the file. Since the directory table does not have automatic backup function, if the directory is damaged, Lost a lot of files. A method to reduce the loss is also to use the above method of chkdsk or scandisk to search for the chk file from the hard disk. When the directory table is damaged, the first cluster number is lost. In the case where the fat is damaged, the chk file is generally formed. Relatively complete file data, each chk file is a complete file, change it to the original name to recover most files. 9. Data recovery when deleting partitions by mistake. After deleting the hard disk partition with fdisk, the surface phenomenon is The data on the hard disk has completely disappeared, and entering the hard disk when it is not formatted will display an invalid drive. If you understand how fdisk works, you will know that fdisk just rewrites the contents of the hard disk's main boot sector (0 side 0 track 1 sector). Specifically, the hard disk partition table information is deleted, and the data of any partition in the hard disk has not changed, and the above-mentioned partition table error repair method can be copied, that is, the method of restoring the partition table data can restore the original partition, that is, the data, but This is limited to after partitioning or rebuilding partitions. If the partition has been formatted with format, after restoring the partition first, the partition data is restored as follows. 10, the wrong formatted hard disk data recovery In the DOS high version state, the format operation format in the default state has been established to restore the formatted disk information, in fact, the disk DOS boot sector, fat partition All the contents of the table and table of contents are copied to the last few sectors of the disk (because the latter sectors are rarely used), and the contents of the data area are not changed at all. In this way, by running "unformat c:", the original file allocation table and directory table can be restored, thereby completing the recovery of the hard disk information. In addition, DOS also provides a miror command to record the current disk information for recovery after formatting or deletion. This method is also effective.