XP is wrong... LOL I wouldn't expect the newest hardware, such as P55A series boards and their components to work well with an OS build from several years ago. You might be able to get it to work, but the only thing I can think of trying is installing it with AHCI enabled in the BIOS before you install XP. Maybe XP can't handle that - I am not sure. Just ditch XP ASAP. Win 7 is as good at what XP did, plus a lot more. Sorry to suggest spending more $$.