Seriously!!!!!!! I have this very same problem! Please help out.
I have made an ISO bootable usb drive on a 32gb sands. I made sure it was formatted to fat32 one time and expat the next. the exact image from the windows site is on the usb.... yet when i go to the asus pc using a asus x77 motherboard no matter what i change the settings to, no matter if i turn off safe boot, if i force it to boot from the usb, if i tell it the usb is a hdd, if i tell it the usb is a cd-rom, if i change it to look for UEFI usb drives, if i tell it to look for legacy usb, if I tell it to look for both, if i turn the CSM on or off or auto, NOTHING WORKS
EVERY SINGLE TIME no matter what random variant of those different BIOS options i change to, going off of 100's of youtube videos and forum posts, it NEVER EVER finds anything on the USB... I get that SAME error message every single time without fail. "reboot and select proper boot.....blah blah blah"
this is insane.
ASUS created the crappiest motherboard that has ever existed I guess. I should have just shelled out the extra $400 for a new motherboard and a 9th gen chipset but i got this x77 MOBO and a i7 2600k for nothing so i want to use it... but this BIOS has (oh and by the way it IS the latest bios from ASUS, version 2104 i think) the worst UI i have ever seen
one thing that is weird is unless select the USB and force it as boot option 1, it doesn't automatically seem to find it in the ASUS EZ mode...
like if i start from scratch, put all the ASUS settings back to stock, plug both my ssd that is brand new and blank in to the Sata port and then this windows.iso USB in to any random USB 3.0 or 2.0 port (i have tried them all) when i open up the BIOS (again this is the BIOS reset to factory default) the EZ MODE page that appears first only EVER shows my SSD drive. It never recognizes the USB in EZ MODE...... its only after i go in to advanced mode (its always visible in there)
so, idk if that's relevant, probably not....
this is just crazy, i am usually completely competent on a computer, so i KNOW this is an ASUS problem or somehow the usb i am making isn't able to be read...
I know my APPLE IMAC is making the USB installer using bootcamp... and that APPLE creates these things as UEFI.... but that shouldn't matter.... I am telling the ASUS BIOS to look for UEFI usb drives!!!!!!!!