OK a little off on your post, but I think I figured out what you are saying.
Let me Guess...
You built a new rig and it has a SATA card built in on the motherboard?
You are booting from the XP CD and it cant find the hard drive?
You need to first locate the floppy disk that came with your motherboard. (Shouls be labeled SATA driver.
If it didnt come with one then you need to take the CD that came with it and put it in a PC that is running. Locate the driver on the CD and copy it to a floppy disk.
Now boot from the XP CD. Tap the F6 when you see at the bottom (F6 to add 3rd party SCSI or RAID drivers.)
After it loads some more stuff it will prompt you to enter the floppy disk.
Insert the disk hit ??? I think its S to load the driver? pick the driver. hit enter.
It will load the driver.
(Note: when you copy the files from the CD to the floppy copy the contents of the directory not the full directory. OEMSETUP, all other files and all folders should be on the root or the floppy.)