Hard drives are mounted differently in desktop computers than in laptops. Desktops have dedicated slots in the front of the computer case for 3.5-inch devices, including hard drives. Laptops vary by brand and type in where the hard drive is mounted. The manufacturer’s manual should contain this information.
If the hard drive inside a desktop computer is obscured, it is easiest to find and follow the Sata cable that connects the drive to the motherboard. This flat cable is about half an inch wide and, almost always, bright red.
Desktop computers can, in principle, have a hard drive connected anywhere inside the case, as there are a number of ways to fix one to the computer case frame. It is, therefore, possible that you may find multiple hard drives in various locations inside the computer case.
For laptops there are space constraints, that is why the location of the hard drive is dictated by the design. Another difference is that, at 2.5 inches wide, these hard drives are physically smaller than their desktop counterparts.
When you access any electric device, make sure that the power (as well as any laptop battery) is disconnected. When you work with electronics, it is advisable to use an anti-static bracelet to prevent damage. Also, be aware that opening a computer might void its warranty.