The hard drives built into most laptop computers have smaller capacities than the ones in new desktop computers because there is limited space on the platters inside the drives. Therefore, the drive inside your laptop will probably fill up relatively quickly with program and data files.
It's possible to replace the original drive with a new one that has more space, but moving Windows and all your other programs to a new drive on a laptop is a major project because it requires a special adapter to transfer files from the old drive to the new one. So the best way to increase the amount of storage your computer can use is to connect a second, external drive to the computer through a USB or IEEE 1394 (FireWire) port or a PC Card.
For large data files, such as the ones that you might create during an audio or video recording project, and for files you don't use when you're away from your home base, a full-sized hard drive is the better choice. On the other hand, if you want to offload a few text or data files at a time, you can use a pocket-sized flash drive or hard drive. Both types can be convenient for using the same data files with more than one computer.
When you connect an external drive to your laptop, Windows should immediately recognize it and add it to the list of drives in My Computer and the finders that appear when you use the Save As command in many programs. As far as Windows is concerned, the external drive is just another place to store and read data; you can treat it the same way you treat the computer's internal drive.
External hard drives are sold in two forms: preassembled ready-to-run Plug-and-Play drives, and enclosures that hold standard IDE or SATA drives. If you don't mind spending a few minutes to mount a drive inside an enclosure and run the formatting program supplied with the drive, a do-it-yourself enclosure can be the more economical approach; but if you prefer a simple and convenient hookup, the preassembled version is the obvious choice.
Flash drives are compact modules that store data in nonvolatile memory and that connect to your computer through a USB connector or a PC Card or ExpressCard socket. Because many flash drives are small enough to fit on a key ring or a chain that you can wear on your wrist or around your neck, they're a good way to carry extremely sensitive or confidential information that you don't want to store on the computer's disk drive, or to carry data files from one computer to another (for example, from home to office, or from your own computer at home to a public computer in a library or classroom).
Both USB drives and PC Cards are hot-swap devices, so you can connect or disconnect them without the need to turn off the computer.