Most laptops have a bay for the hard drive allowing access to them should you need to replace or upgrade them. Laptop drives are 2.1 inches wide and are quite thin at less than a centimeter in thickness. Older laptops utilized a thinner version of the IDE connector like a miniature version of it’s bigger kin. Today’s SATA drives use a connector that allows it to interface with the on-board connectors which can be done only if the manufacturer has considered such in its design.
Though standardized in design, there may be slight differences in the bay design which can be proprietary for some manufacturers. These portable computers are also limited as to the maximum size of disk that can be connected to them due to the bios programming that has been done when they were made. They can however accept both types of drives, with 5,400 and 7,200 rpm drives being the most common.