The hard drive in a computer is permanent memory. It is what holds your personal files and the computer's operating system. Programs on your computer are installed onto this internal disk and can be used at any time in the future. Hard drives are only storage space, like a filing cabinet. A common question we are asked is if having too many programs installed on the hard drive will slow a computer down. The answer is that having a lot of files on your drive does not cause your system to slow down. Programs and files on your hard drive are not necessarily running simply being stored for later use.
Hard drives, unlike the other PC components is a mechanically spinning disk. This physical movement is thousands of times slower than the rest of the computer and so it is important to get a drive that will run as fast as possible. There are some things that pertain to hard drives: size, RPM, and cache.
The size of your disk is the total amount of space you can use to install programs, and save personal files. From pictures, email and videos, to music, games, and even operating systems. The larger the size, the more info can be stored.
Cache and RPM will affect the speed and performance of your computer. Having a higher cache (on disk memory), and faster RPM will increase the speed of the disk.