Most new computers come with a single hard drive to store programs and data files. You can expect the dealer or manufacturer to format the drive and load Windows and other software before they deliver the computer.
The important characteristics of a hard drive are
The amount of data the drive can hold (expressed in gigabytes)
The speed at which the magnetic disks rotate inside the drive
The buffer that stores copies of recently read data
The type of interface between the drive and the motherboard
Before you buy your computer, it's a good idea to ask about the hard drive's capacity, speed, buffer, as well as its interface. It's quite possible that the salespeople, especially in a retail store, won't know the answers to your questions, but they should be able to tell you where to find out.
Look for more information about hard drives in Chapter 9, including instructions for buying, installing, and using a second drive.
A hard drive with a relatively small capacity costs less than a drive with more space, but when you calculate the cost-per-gigabyte, the larger drive might be more of a bargain. If you expect to store very large audio, video, or graphics files on your system, look for a computer with a big drive (at least 200GB for a desktop system). If you're buying a machine for your office that only needs to store relatively small text and data files, a smaller drive might be all you need. Hard drives for laptop computers are physically smaller than the ones inside desktop machines, so the maximum capacity is also smaller.
See Chapter 1 for more differences between laptop computers and desktops.
Don't assume that a home computer doesn't need a big drive. If you or your children play games with complex graphics or download MP3 music files and podcasts, the drive can fill up sooner than you think. And don't forget all those pictures that you transfer from your digital camera. It's a good idea to get a hard drive with a generous capacity in your new computer, but don't worry about underestimating your ultimate requirement. When the original drive comes close to filling up with data, it's easy enough to add a second drive.
Most new hard drives come with internal disks that spin at 7200 RPM (revolutions per minute) or more, but you might find a slower 5400 RPM drive in a less expensive computer. Obviously, faster is better, especially when you're working with very large files, because a fast drive takes less time to locate individual files. A computer with a faster drive loads Windows more quickly when you turn it on, and reduces the amount of time needed to open and store files and perform other common maintenance tasks.
The disk cache, or buffer, is a temporary storage area on the drive that holds copies of data that the computer recently read, and expects to read again in the near future. When the drive reads data from the buffer, it is able to transfer it to the CPU more quickly because it doesn't have to spend time searching through the whole drive for the file that contains that data.
Most drives used in desktop computers have either a 2MB buffer or an 8MB buffer; some very large drives have 16MB buffers. A 2MB buffer is adequate for things like office work, e-mail, and Web browsing, but a larger buffer improves performance on video games and in servers that have heavy workloads. An 8MB buffer is a better choice for a laptop computer.
The interface is the system that the computer uses to exchange data with a disk drive. Your new computer should use either an IDE interface (also called an ATA interface) or an SATA interface. SATA drives were introduced more recently than the older IDE types, but the drive manufacturers still make both types. The computer's motherboard probably has sockets for both interface types if it's a desktop system.
If you have a choice, ask for an SATA drive, but don't worry if IDE is your only option. In today's computers, the difference in performance is insignificant, but SATA drives accommodate the faster processors and other improvements that may become available in the near future. In addition, SATA cables are more compact than the ones on IDE drives, so they make it easier to work inside the computer case.
Chapter 9 discusses the difference between IDE (also called ATA) and SATA interfaces.