Master slave notebook drive

ACHI - Advanced Host Controller Interface http://en.wikipedia.org/wiki/Advanced_Host_Controller_Interface

Your title says Master and Slave, unless your running a fairly old machine (pre 2006), your PC will more than likely be using SATA Hard Disk Drives, not IDE - so Master and Slave will be irrelevant.

Your should leave your PC in ACHI unless your switching to RAID. If you really wish to disable it, this can be done in the BIOS.