A couple of things -
The Dell US website has this in the spec. section for the XPS 710:
The XPS 710 supports up to four hard drives4, each with up to 750GB space - a potential capacity of 2TB total. And with RAID 1 and RAID 0 options, you can choose your storage to meet your needs, whether it's for storing large quantities of files, backing up system information and files, or improving performance with data striping.
Dell will ship up to 3 hard drives.
* Up to 2TB5 Multiple Serial ATA Hard Drives (all 4 drives utilized)
* Up to 750GB3 Single Serial ATA Hard Drive
Are you sure that 1TB disks are supported?
Secondly, XP does not support SATA disks "out of the box" - you have to supply the SATA drivers at installation time, IIRC.
Vista does "natively" support SATA disks.
So I guess my question is - is it a SATA disk? And does the PC BIOS support it?
I would search for articles on installing XP on SATA disks - possibly without access to a floppy drive (if that's your scenario), but you can get around that by slipstreaming the drivers onto the XP install CD - might as well slipstream SP3 while you are at it!
SD