The option rom that you access at POST , is a hardware rom, it is either in the firmware for the motherboard, or the firmware for the card. It might be turned On or Off Via the BIOS.
Usually a Raid type of rom is not enabled or disabled via setting a drive unit as raid or not, nor does it change based on the existence of a drive or changes in an OS
It can be effected by the rom update items in the BIOS, where the motherboard bios scans the option roms. It can be effected by the roms on the card, it can be effected by other roms on other cards.
Like many hardware options it could be an item in the BIOS that is turned on or off. When it is a Card item, they sometimes have jumpers or different firmware or firmware changes that can turn the rom itself on or off.
I dont know what exactally the situation here is list of possibles
If it was based only on a option card, and the card is not there, not working or seated improperly or has jumpers to disable it OR its rom. (moved this up on the list, because from what I can tell, it was an option card)
If the rom screen is hidden (low possibility) it is just harder to invoke it via the key command. Dont hold the key keep hitting it over and over again.
Wrong command, it isnt I (rarely they move a key because of a conflict) , read the manuel < while reading check for a On/Off board Jumper settings, that might exist.
If the BIOS has been adjusted to shut it off (higher chance) Just go through the bios finding items that would turn it on (it is on the MB bios), for cards allow for a refreshing of the other hardware roms in the bios.
If a firmware change has been made to disable/remove it (happens but rare), Check for 2 firmware types for the motherboard or card bios at the manufactures site.
If the Rom for that has been damaged, not much you can do, but use it based only on the OS drivering, which works fine, except for when your not in that OS.
If the ROM(s) gets in a bios based Memory situation. in rare but painful cases, the amount of memory that each option rom uses , and the amount of memory that the bios leaves for it. This happens when you install it and the option rom never fit, or when changes are made to either rom and they both no longer fit. Also can happen when you add in another hard ROM that is used at post (another piece of hardware using a rom). Requires a different flash, or removing one board, or manufactures workaround.
If it is just a problem of installing, XP doesn't have that instantly available during install, you had to load a driver for "scsi" at install.
If you need more information, then more info about the system or what your seeing, or if there is a option card, what the option card is or was, what cards are in it, etc.