How to fix boot block

Updated April 17, 2017

Boot block occurs when the BIOS of a computer is enable to start up correctly. The BIOS is the on-chip set of instructions that starts up automatically on power-up. A computer needs an operating system and it is the BIOS’s job to load that operating system. If the BIOS shuts down, your computer is effectively dead. There are two reasons for a boot block. One is that the initialisation procedures of the BIOS has detected a hardware fault and will not proceed until that problem is fixed. The second is where the BIOS software has become corrupted. Each computer manufacturer has specific procedures for recovering from this situation, but they usually have the same elements in common. Lenovo includes recovery software on a disc and requires adjustments to be made to the physical chip inside the computer.

Turn off the computer, unplug it and remove the battery if it is a laptop. Wait a few minutes for the power to drain out of all the circuits and devices inside the computer.

Locate the screws at the back of the CPU or underneath the laptop and remove the cover. If you are recovering a laptop, the underside covering should come away.

Look for the Clear CMOS/Recovery jumper. For Lenovo computers you can find this in the system board diagram (see Resources). Move the jumper from pins 1 and 2 to pins 2 and 3.

Put the cover back on the computer, screw it back together. Reconnect the power lead.

Insert the POST/BIOS update diskette and turn the computer on. If the monitor has a separate power switch turn that on as well. The monitor will not show anything. You will hear a series of beeps. This indicates that the update is proceeding. Wait for the beeps to stop. Remove the diskette and turn off the computer and the monitor.

Unplug the computer, remove any battery and wait for power to ebb out of the system. Remove the cover and return the jumper to pins 1 and 2.

Replace the cover and any batteries and power chords. Turn on the computer and it should start normally.


If the boot block was caused by a hardware failure, this method will not work. The only way you can sort that problem out is to take the computer to a repair shop.

Things You'll Need

  • POST/BIOS update diskette.
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About the Author

Stephen Byron Cooper began writing professionally in 2010. He holds a Bachelor of Science in computing from the University of Plymouth and a Master of Science in manufacturing systems from Kingston University. A career as a programmer gives him experience in technology. Cooper also has experience in hospitality management with knowledge in tourism.