Hit F2 at power-on to get into the BIOS that identifies itself as the "BIOS Setup Utility". Mine is fitted with Version 1.00D.2456, dated 01/22/10.
I found very little on the Fujitsu support pages for the S100 other than some standard bits of documentation.
In the BIOS, under the Security tab, you have the option of Boot from USB Devices that can be set to Enabled or Disabled.
Moving on to the Boot tab this shows you what the system has detected as it powered up. In the first instance this was just:
After plugging in a SanDisk USB pen drive and a 1GB Compact Flash card I got:
As usual you can use the +/- keys to reorder
You can also get straight to these options by hitting the F12 key on power-up.
I had no problems with booting off an 8GB SanDisk USB pen drive nor installing and using a 1GB Compact Flash card.
Any comments? email me. Added November 2019