Your hard drive has a number of magnetized platters connected to a spindle. The spindle spins the platters at a very fast speed while a series of read/write heads scan over them both looking for and writing information. This information is transferred via a cable system, or through a wireless connection to a hard disk controller, which in most systems is built into the motherboard, or in some systems installed as an add-in card. The information that comes from your hard drive through its controller is then made available to the components of your computer. The effectiveness of your hard drive (its performance) depends on how much of its capacity remains unused, how well organised the data is (known as fragmentation) and its data transfer rate, which in turn is dependent on its connection type and the drive's spin rate.