Download: USB Disk Storage Format Tool
Download: Windows 98 MS-DOS boot files
Extract the USB Disk Storage Format Tool and the Windows 98 MS-DOS boot files to your harddrive.
Double click on the 'usb_format.exe'.
Select your USB drive.
Select 'FAT32' for the file system.
Add a 'Volume Label'.
Select 'Quick Format'.
Select 'create a DOS Bootable Disk'
Click on 'Browse' and add the 'win98boot' folder you extracted to your harddrive.
Should look something like the screenshot below.
When it is finished close the format tool and copy over your CTXXM.EXE firmware file to the root of the USB drive.
Reboot and enter your BIOS and select USB as your first boot choice, save and exit.
It should now boot to MS-DOS from the USB drive where you can now run the CTXXM.EXE update.
For this to work will depend on the USB drive and BIOS support for bootable USB media.
The firmware CTxxM.EXE files can be extracted from the .ISO file using WinRAR.