XP didn't support SATA hard drives prior to the SP3 update, so you probably need to go into your BIOS setup and disable AHCI which will allow your hard drive to run in IDE mode. I assume you've researched and download the XP drivers you'll need because your devices including your network adapter may not work without them.
I couldn't boot from the XP CD until I used EasyBCD to delete the Windows 7 boot thingy (something I found googling). After that, I was able to format a drive and then it begins to 'copy files to the windows installation folders'. After this, it prompts to restart. But when I restart and boot from CD (all I can do), I get back to the list of drives to install windows on, with no progress. Any suggestions on how to get past this endless loop?