I use the old Hewlett Packard flash utility which used to be free on the internet, to load system files to make the drive bootable. It requests a location for boot files, and I have another file with the contents of a Windows 98 boot floppy copied to it. The HP ulitility copies those files to the thumb drive.
so, the trick is, you need to "sys" the drive. Now you have the information you need to google a utility for that purpose.