First, make sure the RAID chip is enabled in the BIOS. You should see a separate BIOS for the array at boot-up where you can actually set up the array. If you don't see this, the XP install won't either.
Yes, your motherboard may not have come with a floppy, but the drivers should be on the CD that came with the board. You will have to copy them to a floppy and install them when prompted. Some motherboard makers bury these drivers so deep in folders that it can be difficult to figure out the correct files to copy. Make sure they are for your OS (XP) and if you don't see a file with the .oem file extension you most likely have the wrong ones. Sorry if this is confusing, but I don't make motherboards.
Also, many newer boards have provisions for two separate arrays. Running off of two different chips. You need to make sure you are installing the drivers for the chip that the array is actually on.
Hope this helps.