OK. To remove some variables....
1. Always switch off the laptop each time before you test a 'scenario'.
2. Always try all the USB ports (switching off after each test) - not all ports are the same.
3. You can use RMPrepUSB to check if a drive is removable or fixed (Windows 10 will show as Local Disk or USB Drive)
4. You can use RMPrepUSB - Drive Info - 0 to view the MBR partition table of a USB drive
If two USB devices seem to be needed - which USB ports must be used and where? For instance, the BIOS may not be looking at USB Port 1 ON A WARM RESTART but may only be looking at USB Port 2.
For instance, on my Lenovo IdeaPad 300, the bootable USB flash drive in the left-hand USB port of the laptop (USB 3) is only detected on switch on - but if I reboot/reset the laptop then it is not detected - however, if I plug the same USB drive into the right-hand USB port (USB 2), it is always detected (even after a warm reset). So if I want to use the left-hand port (which is USB 3) - I must remember to always switch off the laptop and switch it on again because a warm reset\reboot will fail to detect it!
Some BIOSes only detect the type of USB drive on power-on - if you do a warm reset\restart\ctrl-alt-del then they just treat the USB drive in the same way as they did on the first power-on boot! This means you must switch off the power and then switch it on again each time. It can get very confusing if you don't do this (for instance you could change the contents of the same USB drive and it would not be re-detected if you just used Ctrl-Alt-Del to reboot or may be detected as the same initial type when you have actually change it to a different type - e.g. 'FDD/ZIP' with no MBR vs. 'HDD' with MBR).
If there is any BIOS option, USB HDD should be used (but this is not usually found in laptop BIOSes).
1. Always switch off the laptop each time before you test a 'scenario'.
2. Always try all the USB ports (switching off after each test) - not all ports are the same.
3. You can use RMPrepUSB to check if a drive is removable or fixed (Windows 10 will show as Local Disk or USB Drive)
4. You can use RMPrepUSB - Drive Info - 0 to view the MBR partition table of a USB drive
If two USB devices seem to be needed - which USB ports must be used and where? For instance, the BIOS may not be looking at USB Port 1 ON A WARM RESTART but may only be looking at USB Port 2.
For instance, on my Lenovo IdeaPad 300, the bootable USB flash drive in the left-hand USB port of the laptop (USB 3) is only detected on switch on - but if I reboot/reset the laptop then it is not detected - however, if I plug the same USB drive into the right-hand USB port (USB 2), it is always detected (even after a warm reset). So if I want to use the left-hand port (which is USB 3) - I must remember to always switch off the laptop and switch it on again because a warm reset\reboot will fail to detect it!
Some BIOSes only detect the type of USB drive on power-on - if you do a warm reset\restart\ctrl-alt-del then they just treat the USB drive in the same way as they did on the first power-on boot! This means you must switch off the power and then switch it on again each time. It can get very confusing if you don't do this (for instance you could change the contents of the same USB drive and it would not be re-detected if you just used Ctrl-Alt-Del to reboot or may be detected as the same initial type when you have actually change it to a different type - e.g. 'FDD/ZIP' with no MBR vs. 'HDD' with MBR).
If there is any BIOS option, USB HDD should be used (but this is not usually found in laptop BIOSes).