So I found the issue. Most modern operating system like windows and Linux, when on legacy computers, they use the GPT partition table with a compatibility layer called BIOS BOOT that emulates the Master Boot Record partition table. This works perfectly fine on most computers except this. The solution was to force Linux to install using the MBR partition table and for grub to only install legacy support and not EFI. That also explains why only Rufus USB flash drives were booting.
[IMAGE] [IMAGE]    My uncle bought back in 2011 a Dell Inspiron N7110 made in May of 2010. He gave it to me today because he didn’t need it. The laptop came with windows 7 pre installed but he had upgraded all the way to windows 10. The first thing I did, after I got the laptop and backed up his data in case he needs them in the feature, was to install fedora 37 (my OS of choice). Trying to boot the USB resulted in an error message saying “Operation system not found”. After trying changing some BIOS settings, I decided to try the same but this time burning the ISO with rufus using ISO mode. It booted and installed just fine. Rebooting the computer resulted in the same error message, this time booting from the internal hard drive.   I have tried 8 different Linux distros and windows 10 but everything resulted in the same issue.   I also tried updating the BIOS from A08 to A13 using FreeDOS.   What I find interesting is that the computer won’t boot and give this error message every time unless I’ve created the USB using Rufus.   Any ideas? I’ve already changed a ton of BIOS settings, used different USB flash drives, used different ports.   Thank you in advance!
Old Dell won’t boot any OS.