Holy cow, I wrote a book!
Ian B wondered what the difference is between pressing F5 and F8 while Windows is booting.
I have no idea either. My strategy was to just mash on the function keys, space bar, DEL key, anything else I can think of. Keep pressing them all through the boot process, and maybe a boot menu will show up.
The F5 hotkey was introduced in Windows 95, where the boot sequence hotkeys were as follows:
Man, that's an insane number of boot options all buried behind obscure function keys. Boy am I glad we got rid of them. This frees up room in my brain for things like Beanie Baby trivia.
Bonus chatter: The next generation of computers boots so fast that there's no time to hit any of these hotkeys!