Hard disk logical lock is a very common prank. After the logical lock, no matter what equipment you use, you can't boot the system normally, even floppy disk, CD-ROM drive and dual disk have no influence. Locking principle of "logical lock": When the computer starts the DOS system, it will search the order of all logical disks. When booting DOS, we should first find the partition table information of the main boot sector, and then find the logical disk of each extended partition. "Logical lock modifies the normal master boot partition record and points the first logical disk of the extended partition to itself, so that DOS always finds itself after finding the first logical disk at startup, thus forming an infinite loop. An easier way to open the logical lock is to "hot plug" the hard disk power supply. That is, when the system starts, the locked hard disk is not powered on first, and then the power cord is "hot-plugged" to the hard disk after starting, so that the system can control the hard disk normally. In order to reduce the degree of danger, you'd better follow the following two relatively simple and safe methods after encountering a "logical lock".

★UltraEdit★ Prepare a startup disk first, and then use the binary editing tool (UltraEdit is recommended) to modify IO on other normal machines. SYS file on floppy disk (remember to change the attribute of the file to normal before modification). Specifically, search for the first "55AA" string in this file and modify it to any other value after finding it. With this modified system floppy disk, you can successfully boot from the locked hard disk. But at this time, because the normal partition table of the hard disk has been destroyed, you can't use "Fdisk" to delete and modify partitions.

★DM★ Because DM is a hard disk tool that does not rely on the motherboard BIOS to identify hard disks, even if the hard disk in the motherboard BIOS is set to "None", DM can identify hard disks and perform operations such as partitioning and formatting, so we can also use DM software to unlock hard disks. Copy the DM to the system disk first, connect the locked hard disk, then turn it on, press the "Del" key to enter the BIOS settings, set all IDE interfaces to "None" and save before exiting, and then start the system with a floppy disk, so that the system can start with a lock, because at this time the system is basically equivalent to no hard disk. Run DM after startup, and you will find DM.

Can identify the hard disk, select the hard disk for partition formatting.