Your post is rather cryptic. If I understand it correctly, you are trying to create a DOS bootable USB key to flash your BIOS. Is that correct?
Use this instead: http://files.extremeoverclocking.com/file.php?f=197
and download both the HP utility and the Windows 98 system files. Then execute this commande from a DOS window:
C:\DriveKey>hpusbf E: -Q -B:C:\temp\dos
Change E: to your USB key drive letter and C:\temp\dos to the location where you extracted the Windows 98 system files. Then boot from it. I tested it on one of my systems and it booted to DOS.