This issue may be related to the BIOS mode that is set on your computer. You will need to check your system BIOS settings to ensure your system is set to Legacy mode or that UEFI is disabled. Here is how you can check your BIOS settings.
At the moment of turning on your computer, you will see an option to enter SETUP. Depending on the manufacturer of your system, you can press the DEL key, the F2 key or another key that is listed on screen to access the system BIOS. If you are not sure, consult the User Guide that came with your computer or call the manufacturer's technical support for assistance.
Once in your system BIOS, look under the Boot menu to find an option that reads "UEFI/BIOS Boot Mode" or "UEFI Boot". In the case of "UEFI/BIOS Boot Mode" switch the mode from "UEFI" to "Legacy" mode.
If you see "UEFI Boot", switch the option from "Enabled" to "Disabled". Be sure to save your BIOS changes and exit to reboot your computer. You should now be able to boot up from Active@ Boot Disk.
Once you have completed your operation with the boot environment and reboot your system, remember to go back into the BIOS and switch the boot mode back to UEFI.
For information about which device your system should boot from, please read more:
The system BIOS (system configuration) provides the option for setting the BOOT PRIORITY (start-up sequence). You may need to change the BOOT PRIORITY to specify the device you would like to start from first. Depending on the manufacturer of your system, you can press the DEL key, the F2 key or the F12 key the moment after turning on the computer's power. Some systems allow you to change the BOOT PRIORITY on power-up simply by holding down the F key for floppy or the C key for the CD-ROM device. If you are not sure, consult the User Guide that came with your computer or call the manufacturer's technical support for assistance.
ADDENDUM: If you are not able to switch from UEFI mode or noticed that you cannot boot into the boot environment, then you will need to also look for an additional option in the BIOS called Secure Boot. Check your BIOS for a SECURITY section and disable the SECURE BOOT option.
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