First realize that Dell's have a lot of proprietary hardware and may need some drivers installed to function correctly with all your hardware.
When you say that Red Hat does not see the XP disk, do you mean that the cd does not boot, or that XP does not see the hard disk? XP can't see disks partitioned with Linux filesystems. You would need to use a Red Hat boot disk to re-partition the hard drive free of the Linux filesystem, then install XP. The other option is to use the hard drive manufacturer's utility to rid the drive of the Linux partitions. Then install XP.
If the system is set to boot from the CD first and it does not do so, then there is another problem. Red Hat does not take over until the bios loads the actual bootloader.
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"I love it when a plan comes together." - Hannibal Smith