Fix Operating System Not Found Error
When powering up you computer, you may encounter the following error: "Operating System not found". This boot problem is related to the MBR signature 55 AA.
This article explains step by step, how to fix Operating System Not Found error. Operating System Not Found Windows boot problem can be fixed quickly and easily using Emergency Boot Kit.
1. Symptoms of the problem
When computer is powered up, an error message "Operating System not found" appears (white-on-black letters in text mode and blinking cursor):
2. Normal boot sequence
Normally computer boots as shown below (Windows 7 boot sequence is shown as example):
3. Defect in the boot sequence which leads to Operating System Not Found error
Defect in the boot sequence which is a reason for Operating System Not Found error is shown below:
4. How to fix Operating System Not Found error
1) Download Emergency Boot Kit and deploy it to USB thumbdrive according to the instructions, then set up your BIOS to boot from USB thumbdrive. You need full version of Emergency Boot Kit to actually write changes to the disk, but it's recommended to try demo version to make sure there are no hardware incompatibilities.
2) Boot from Emergency Boot Kit, wait until the main menu appears.
3) Find boot loader for your primary OS in the list. Please note that "called by BIOS" radiobutton is off:
4) Click on the radio button "called by BIOS" for bootloader of your primary OS. It should be turned on now:
5) Click OK to close the window and then choose "Reboot" in the main menu. 'Operating System Not Found' boot problem is fixed now.
Please note: Mount & Boot Center verifies entire boot path from BIOS to the OS boot loader, so other boot problems may be automatically fixed at this point.