With Windows running place the software cd that came along with the board in your cd or dvd drive as well as placing a blank floppy in that one. Once the opening menu loads you will see the option to create a driver floppy for installing sata drives. This is the way Asus has their software setup. When the next opens you will have the option to create the disk right then where the list of Windows versions is shown like XP 32bit, XP 64bit, 2000, ME. 98. The other option is to format the disk. Use that first. For some reason the XP installer will load the drivers copied later a lot easier this way.
Once the floppy is formatted proceed with the option to create the driver disk and then boot from the XP once you have that in the drive. Right when the first screen comes up the option to press the F6 key for installing sata/raid will be seen at that time. So press that button right away. This will then proceed to load the drivers from the floppy. If any didn't copy to the 3 1/2" from the board cd you will see that error message appear soon.
The alternate way is to first boot with the board's cd to create the driver disk when that screen comes up. For some reason you are more likely to the error message about one driver and have to redo it all over again. When the drivers are sucessfully loaded the XP installer will reach the screen where you choose between pressing R for the recover console or enter to start the installation going. Once in the following screen you should readily see the dirve plainly listed by make and model number along with the total drive space available. If you want more then one partition you simply lower the total seen in the counter there. Either way the installer will then create the new partition if needed and format it for the copy of the setup files to the drive. Aftwards you simply reboot and hopefully have the drive set as the first in the boot order.