Changing between AHCI or IDE

there should be a registry key edit way when on the OS to switch from IDE to achi.

I don't think so. XP won't load in AHCI because it isn't supported and Win & won't boot in IDE because it wasn't set that way when installed.

YOu could try and hook up one of the hard drives to a different controller if you have two.

Or you could try changing Win7 to use IDE in the registry, but I don't know if that will work, since everyone goes the other way with the registry entry. ie turning AHCI to on.

http://www.mydigitallife.info/how-to-enable-ahci-suppor...

I would go with the different controller port (assuming your motherboard has more than one  ) and go from there. With it being a laptop though, all the ports may be in use by the existing drive and the CD/DVD possibly.

Even though you have the drive partitioned, it still will require the switch to be thrown before you'll get functionality out of your desired OS. Had you considered running XP inside of VirtualBox? It would relieve the headache of having to change the BIOS setting and you could essentially do the same thing you are wanting to do with the separate partition.

You should be able to run Windows XP in AHCI mode once the appropriate Intel RST drivers are installed and the registry change is implemented. You should also be able to install it in AHCI mode if you provide the RST drivers at install time.

Didn't work for me though. I tried that for about 2 hrs one day on a new install. Had the right drivers but it just wouldn't work. Was disappointed that I had to set my new SATA drives on IDE mode.

Try reinstalling it in AHCI mode to begin with by providing the drivers manually using F6 at install time.

Alternatively you could just get with the times and run everything on Windows 7 or 8 like the rest of us.

If you have particular use cases that absolutely require you to use Windows XP without exception, use a virtual machine instead.

eek, sorry that I missed the "laptop" part. It won't have the two controllers to do that with.