With an internal hard drive (HDD), you can store photos, movies, videos, and other files. There are internal HDDs for desktops, laptops, and NAS servers. They have a 2.5-inch or 3.5-inch size. The 2.5-inch drives are suitable for smaller laptops. You often use a 3.5-inch drive for a desktop or NAS. Choose an internal HDD of 8TB or higher if you store many large video files or demanding games.