OK, so I tried to put a compatible hard drive from a Dell Inspiron 9400 into a Dell Inspiron 1720 and all I get is XLDR ATA ERROR. I have searched but don't quite understand what the exact fix is. I tried to boot from CD with a slipstreamed copy of XP, but it found no hard drive. Not sure if the HD even works, but the laptop that it came out of just bluescreened one day and I bought a new HD and it did not work either, so I just assumed maybe it was the motherboard or something other than the HD. So, I think this HD is good. Is there a way to fix this error in the BIOS of the laptop I'm trying to put it in? or any other solution. I see where the SATA operation is set to AHCI in the BIOS. Should I change it to ATA in the BIOS of the 1720??