Windows 10: Determine whether a usb drive is bootable

Short of rebooting, is there some way to tell whether a usb drive is bootable?

tcebob said:

Short of rebooting, is there some way to tell whether a usb drive is bootable?

Not really. Some cheapie media thumb drives can't be made bootable.

If a good thumb drive was created with a legit bootable creation tool and has the normal resources on it, (usually 8 items), it should be bootable.

To be capable of being made bootable a usb stick has to use an mbr partition table. You may not realise it, but a usb doesn't actually need a partiton table, and many are supplied formatted without one. Such a usb has to be reformatted completely from scratch to give it an mbr in order to make it bootable. This is what the MCT does when it makes a bootable usb, you can also do it yourself with Diskpart.

Edwin has shown examples of the contents of a typical bootable usb from Microsoft. The folders boot and efi, and the files bootmgr and bootmgr.efi are essentials, the rest may vary depending on the purpose of the usb. A bootable Recovery Drive won't have a setup.exe or autorun.inf, for example.

In addition, to be bootable on a legacy bios system the partition has to be marked as Active. You can see if it is in Disk Management.

Thanks, all.

EdTittel said:

Thanks for reminding me ... that active + MBR is what it takes to be bootable.

Remember, that's only required for a legacy bios system, a uefi system doesn't care if the partition is active or not - if the right files are there it will boot.