Here's a link onto the ATI homepage which says that that card will work with XP home.
http://www.ati.com/products/radeonx800/radeonx800series/index.html
System Requirements:
Radeon® X800 XL, Radeon® X800 PRO, Radeon® X800 XT and Radeon® X800 XT PLATINUM EDITION require a connection to your PC's internal power supply for operation. Consult your system builder or OEM to ensure your system has an adequate power supply. Otherwise, ATI recommends a 300-Watt power supply or greater to ensure normal system operation where a number of other internal devices are installed.
* Intel Pentium 4/III, AMD Athlon 64/7K/Athlon XP with AGP 8X (0.8v), 4X (1.5V) or universal AGP 3.0 bus configuration (8X/4X) or PCI Express® bus configuration
* 128MB of system memory
* Installation software requires CD-ROM drive
* DVD playback requires DVD drive
Memory Configuration:
* 256MB GDDR3 memory
* 256-bit memory interface
Operating System Support:
* Windows® XP (Home or Pro)
* Windows® 2000 with Service Pack 1 (or later)
* Windows® Media Center Edition
Warranty:
* 3-year limited
Display Support:
* VGA connector for analog CRT
* DVI-I connector for digital CRT or flat panel
* S-video or composite connector for TV/VCR
* YPbPr connection to HDTV
* Drive two displays simultaneously with independent resolutions and refresh rates