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#1710
Have you considered virtualizing XP from within Win7 using freeware like XP Mode, Virtual Player, VMWare, Virtual Box. It's a lot easier than trying to install XP on new hardware.
When I google XP Home OEM SP3 or XP Home Retail SP3 downloads I get links to several downloads. If you use a torrent I'd read the comments to make sure nothing is added, especially an illegal activation crack, since you have the Product Key to use.
If an SP3 installer doesn't work outright then you'll need the SATA or Storage controller driver which is a component of the chipset, which can be found on the computer or mobo maker's Support Downloads webpage for your model. SATA Drivers - Slipstream into Windows XP CD