file name: ubuntu-18.04.1-desktop-amd64.iso. currently windows 8.1 installed on my laptop. I am trying to install ubuntu from usb flash drive and created a bootable usb using rufus. When I boot from usb it gave me four options. try ubuntu, install ubuntu, oem install and check disk

when I select the option 1 (try ubuntu) or option 2 (install ubuntu) then it gives me an error message saying

18.206119 Problem Loading UEFI:db X.509 certificate (-65)

enter image description here

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    It is probable that it is related to secure boot. When you restart your PC, enter to BIOS options then disable secure boot and see if the error still exists.
    – singrium
    Sep 5 '18 at 10:04
  • @singrium, it is related to secure boot. Do you have any suggestion on how to resolve the issue? Jul 28 at 21:18
  • @MahendraGunawardena You can disable that from the BIOS menu.
    – singrium
    Jul 29 at 8:06
  • @singrium, I have secure boot disabled and still have the issue, I have posted my question here Jul 29 at 11:30

I've had the exact same error message while trying to install Lubuntu. I solved it by changing the BIOS boot setting to a setting that was not UEFI ; CSM in my case. My laptop is a Toshiba C855D-S5303. Am AMD Dual-core 300E. Although I still recieved an error message about "no IRQ handler" Lubuntu would install.

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