If SATA, you either get to present a driver during the installation process when XP asks for 3rd party drivers or you change your MB BIOS to a PATA compatibility mode. If this isn't your problem, please offer more about the hardware you're trying to install XP on.
I've installed XP many times and this is the first time this has happened to me. After XP copyies the files and reboots it wants to reload the cd which, of course, I ignore. Then it just hangs or, ultimately, gives the message, "Operating system not found." I tried the installation with only the one drive connected and tried installing it to a single partition on that drive. Any ideas what could cause this to happen would be appreciated?