nLite has a lot of options you do not need, especially if you haven't used it before.
-- Copy your XP CD to a folder (MyXP for example)
-- As Jaquith linked, get sp3 and save it to a folder (sp3, for example).
-- Extract your RAID driver from the motherboard CD (or the mob's support website) to another folder (RAID driver, for example).
-- On open nLite, browse to the folder MyXP (the folders and files you copied from your original XP CD).
-- After nLite finds the folders/files, it will open the Task Selection: click on Service Pack, Drivers, and Bootable ISO.
The next screen allows you to choose sp3, you may have to browse to the folder you saved it.
The next screen is Drivers. Choose Insert single driver and browse to the folder with your RAID driver and click on that file. You will have to choose the driver you want: ICH8R.
When that is done, nLite will ask you if you want to start the process. Choose yes. nLite will create a bootable iso image. Then it will ask you if you want to burn the image to disk. Choose yes, and insert a clean CD or CDRW into your ODD. nLite will burn the image. When it is complete you can use that disk to install XP on your boards' RAID volume.