source

Start a command line utility called diskpart. This can be done directly from start/run or from a command prompt. Comments are between {}.

diskpart {This will start diskpart from a command prompt}
list disk {This will list all available disks in the system}
select disk 1 {This will select your usb disk, if it is called 1 in your system}
clean {This will erase ALL information on the currently selected disk}
create partition primary 
select partition 1 
active 
format fs=fat32 
assign 
exit

Now we need to copy the boot sector.  Make sure that you are still within the command prompt window

D:  (this is moubnted ISO image as a CD of the WIndows server media)

cd boot

Note: Run “bootsect /help” for detailed usage instructions.

bootsect /nt60 e:

Target volumes will be updated with BOOTMGR compatible bootcode.

Bootcode was successfully updated on all targeted volumes.

When you are finished with diskpart, all you need to do is copy all files from your Windows Vista / Windows Server 2008 installation media to the usb disk.

xcopy d:\*.* /s/e/f e:\

, 2016

To create a bootable USB flash drive

Advice from Dell

Windows 2016

To create a bootable USB flash drive

1. Insert a USB flash drive into a running computer.

2. Open a Command Prompt window as an administrator.

3. Type diskpart.

4. In the new command line window that opens, to determine the USB flash drive number or drive letter, at the command prompt, type list disk, and then click ENTER. The list disk command displays all the disks on the computer. Note the drive number or drive letter of the USB flash drive.

5. At the command prompt, type select disk <X>, where X is the drive number or drive letter of the USB flash drive, and then click ENTER.

6. Type clean, and the click ENTER. This command deletes all data from the USB flash drive.

7. To create a new primary partition on the USB flash drive, type create part pri, and then click ENTER.

8. To select the partition that you just created, type select part 1, and then click ENTER.

9. To format the partition, type format fs=ntfs quick, and then click ENTER.

    Important

   If your server platform supports Unified Extensible Firmware Interface (UEFI), you should format the USB flash drive as FAT32 rather than as NTFS. To format the partition as FAT32, type format fs=fat32 quick, and then click ENTER.

10. Type active, and then click ENTER.

11. Type exit, and then click ENTER.

12. When you finish preparing your custom image, save it to the root of the USB flash drive.

source

To create the USB drive to install Windows Server 2019 on BIOS (MBR) systems.

Use PowerShell with Administrative priveleges:

Another explanation how to create bootable USB for Windows 2016 server:

How-to Create Bootable Windows Server 2016 USB Thumb Drive for Installing OS