To install Win XP to a RAID array so you can boot from it, you will use the F6 option screen to allow loading drivers during the early part of the install process. BUT you must be aware that Win XP can ONLY load those drivers from a floppy disk. This means you need a floppy drive in your machine (at least temporarily for the install process) AND a floppy disk with the drivers on it. For that, read the manual with your mobo. In the RAID installation instructions it should tell you where those drivers are - probably on a CD with the machine, but maybe you have to download form a website - and how to get them on a floppy drive. You may just have to copy them, or there may be a small utility you run to write the drivers to a floppy.
I said "drivers", plural. In my case and MAYBE yours, there was more than one driver involved. During Windows Install after you press F6 at the right place, you load one driver from floppy (it shows you the drivers it has found there) and it comes back to the same screen. Then you load another driver. When you've done all you need, that's when you tell it to exit and proceed with the rest of Install.