Dell doesn't post many of the RAID drivers needed to install XP onto a RAID array.  I found the downloads below and was able to install XP Service Pack 3 on to a RAID1 mirror array on a Dell Dimension 9200.

DELL SATA/RAID Drivers:

• Download the self extracting utility, then 'double click' it. You must have a formatted floppy disk ready. Follow the instructions for creating a driver disk. These drivers are only to be used at OS installation (operating setup time) time.

• Insert driver floppy disk before booting onto Windows XP CD. At the beginning of the operating system setup, press F6 when prompted to install a third party SCSI or RAID driver.

• When prompted, select 'S' to Specify Additional Device.

• When prompted, install RAID Driver for RAID configured systems, or AHCI Driver for SATA systems.

 Driver for: Dimension 9100, XPS (Gen 4, Gen5)                  Click Here

 Driver for: Dimension 8400, XPS (Gen3)                               Click Here

 Driver for: Dimension 5150, 9150                                           Click Here

 Driver for: Dimension XPS 600                                               Click Here

 Driver for: Dimension 9200                                                      Click Here