Shulou(Shulou.com)06/03 Report--

This article mainly explains how to solve the hard disk "logic lock". Interested friends may wish to take a look at it. The method introduced in this paper is simple, fast and practical. Next, let the editor take you to learn how to solve the hard disk "logic lock"!

Many computer users have seen or heard that when the hard disk is in the so-called "logic lock", some computers cannot be started with floppy disk, hard disk, or CD-ROM. So, what exactly is a "logical lock"?

The so-called "hard disk logic lock" is made by using an error in some DOS. It uses the technology of "circular partition table" so that some DOS with this error cannot be started with any device, including mobile devices such as floppy disks. When DOS starts, the system will automatically search the information of each partition in the hard disk, such as type, size, etc., so that the system can identify the hard disk, assign it to C, D, E, F and other drives, and enable users to operate on it. The "logical lock" takes advantage of this point, by modifying the partition table of the hard disk to make the partition table loop, that is, pointing the first logic disk of the extended partition to itself, so that some DOS systems can not start because of the endless loop when looking for the partition.

It can be seen that this is actually caused by an error when DOS starts. It is said that as early as 1992, an anti-virus expert named Mike discovered the problem and reported it to the DOS manufacturers with the problem, such as IBM, Novell, DR-DOS/NovellDOS, Microsoft, and so on. Soon after, IBM, Novell and other companies have announced that their new versions of DOS have completely solved this problem, only Microsoft, which owns MS-DOS, ignored it, resulting in the new versions of MS-DOS, such as 6.x, 7.x, etc., still have this problem.

However, because Microsoft's MS-DOS is the most widely used, it also has the greatest impact and harm. Once the user's hard disk is locked by a "logic lock," all kinds of Microsoft operating systems, such as MS-DOS 5.x/6.x/7.x/8.0, cannot start, creating the illusion of hardware failure, and there is nothing even many experts can do about it. As this phenomenon is so terrible that computers will not be able to be used, many people are looking for prevention and solutions. In fact, it is not difficult to solve, here are several solutions.

* Boot using an operating system other than MS-DOS

As can be seen from the above, the "hard disk logic lock" mainly affects Microsoft's MS-DOS system, so it is OK to boot with other DOS. For this reason, I specially tested the boot disks of several practical high versions of DOS, such as MS-DOS 7.10, PC-DOS 7.10, DR-DOS 7.05, ROM-DOS 7.10, FreeDOS beta9, PTS-DOS Pro 2000, in the case of a "logic lock" in the hard disk. The results are as follows:

PC-DOS 7.10 Startup disk: everything is fine when it starts

DR-DOS 7.05 (version number: 7.10) Startup disk: boot everything is fine

ROM-DOS 7.10 Startup disk: everything is fine when it starts

FreeDOS beta9 (version number: 7.10): there is an error in the hard drive during startup and the boot is completely normal.

PTS-DOS Pro 2000 (version number: 6.90): everything is fine when it starts.

Note: all the above DOS are very stable and support FAT32 partition and large hard disk, among which ROM-DOS 7.10 also supports long file name natively and has very good compatibility.

Therefore, any kind of DOS boot disk can be used to boot a hard disk with a "logical lock". Although the drive letter of the locked hard drive (such as C:) is not visible, all kinds of disk partition software, such as Norton Disk Editor 2002, Norton Disk Doctor 2002, and DOS's own FDISK program, can display the locked hard drive. At this time, you can use DISKEDIT and other tools mentioned above to view / manually repair the hard disk, or you can use some software to automatically repair it, such as NetResq, SRCTools, etc., in order to completely remove the "logical lock" on the hard disk, and the data on the hard disk will not be damaged.

* Boot using the repaired MS-DOS boot disk

Although the MS-DOS boot disk cannot start the computer in the normal state when the hard disk is locked, because this is only a BUG in the MS-DOS boot file IO.SYS, as long as you repair this BUG,MS-DOS boot disk will not be affected by the "logical lock" and can start normally. However, even if you are repairing BUG, you should use the correct method. It has been mentioned that the problem can be solved by changing the hard disk partition mark "55AA" in IO.SYS, but this method is very bad. Because, in fact, this method is to let IO.SYS completely ignore the existence of the hard disk, that is, by skipping the hard disk to start the floppy disk, in this way, no matter whether the hard disk is locked or not, the hard disk can not be recognized after booting with this boot disk, so this boot disk cannot be used as a normal MS-DOS boot disk. On the contrary, if you use the correct method to repair the BUG in IO.SYS, after booting with this floppy disk, if the hard disk is good, it can be recognized normally, and even if the hard disk is locked by a "logical lock", it can also be used for further repair after booting with PC-DOS, DR-DOS, ROM-DOS, FreeDOS, PTS-DOS Pro and other boot floppy disks mentioned above (i.e., "starting with a non-MS-DOS operating system"). There are also references to some lower versions of MS-DOS, such as the 3.2 boot disk to boot the computer. But this obviously has many shortcomings, first, the old version of DOS is difficult to find, second, because its version is too low, few features, and poor compatibility; third, these low versions of DOS itself do not support large hard drives (not even 32m), logical partitions, etc., and even cause real damage to the hard disk, and versions such as MS-DOS 3.2m do not even recognize 1.44m floppy disks. It can be seen that the method of starting with a lower version of MS-DOS is not very feasible. Therefore, it is important to use a good method to fix the BUG in the higher version of MS-DOS 's IO.SYS. Take the boot disk of MS-DOS 6.x as an example, simply use any hexadecimal editor (such as PCTOOLS, etc.) to find the hexadecimal string "07 72 03" in the IO.SYS file and replace the last "03" with "06". Other versions of MS-DOS can also use similar methods. For example, the specific modification of IO.SYS in MS-DOS 7.10 can be found in the China DOS Alliance Joint Forum. In this way, Microsoft's MS-DOS boot disk, like other DOS, can boot normally when the hard drive is locked by a "logical lock".

The methods mentioned above are the most direct way to solve the "hard disk logic lock" (that is, "use the DOS boot disk that is not affected by the 'logic lock' to start the computer"), and it is also the best way. Therefore, just make one of the boot disks mentioned above (such as PC-DOS 7.10 boot disk, ROM-DOS 7.10 boot disk, FreeDOS boot disk, or repaired MS-DOS boot disk, etc.). This boot disk can be used as a normal boot disk at ordinary times, and when the hard disk is locked, it can be used to boot and solve the problem.

Someone also mentioned other "methods", such as hard disk hot-swappable, DM low frame, etc., which are not only troublesome and dangerous, but also may cause damage to all the data in the hard drive. For example, after hot-swapping the hard disk (it is very troublesome and dangerous to remove the chassis and take down the hard disk, and then reinstall the hard disk after boot), even if you start successfully with the floppy disk, the hard disk will not be recognized at all. Including various hard disk tools. If you use DM to skip BIOS to underframe the hard disk, all the data on the hard disk will be lost, irrecoverable, and the loss will be very large. Thus it can be seen that hard disk hot plug and other "methods" are not practical and feasible.

At this point, I believe you have a deeper understanding of "how to solve the hard disk" logic lock ", might as well come to the actual operation of it! Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

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