Timing is everything in getting to the BIOS changes on these; I've done three and each has its own "quirks." Don't press the Compaq / F-10 key until after the first cursor-drop on bootup or you'll get an error, but if you wait too long it'll move on without you. (Also- remember it's just the Compaq key; I rezapped my first IA-1 three times because I thought I needed a key *combination* to get to the BIOS.)
When you get it right you'll get the language selector; use the up-down arrows to change if you need to, then Enter. That should get you to the main BIOS menu. Use Enter to select, Compaq / F-10 to confirm, and Cancel / Esc to back out. You may have to do this *twice* after inserting a CF card -- once to get the IA1 to recognize the CF, and the second to get it to boot from it.
Each of my IA-1s has been reflashed at least twice, so far with no problems.