A modem is needed in order to connect to a dial up internet connection. A modem can also be used for faxing. Modems can attach to the computer in different ways, and can have built-in processing or use the computer's CPU for processing.
Modems with built-in processing generally include all modems that connect via a standard serial port, as well as any modems that refer to themselves as "Hardware Modems". Software Modems, or modems that rely on the CPU generally include both Internal and USB modems, or have packaging that mentions drivers or requiring a specific CPU to work.
Modems that rely on the CPU are often designed specifically for the current version of Windows only, and will require drivers that are incompatible with future Windows versions, and may be difficult to upgrade. Software Modems are also very difficult to find drivers for non-Windows operating systems. The manufacturer is unlikely to support the hardware with new drivers after it is discontinued, forcing you to buy new hardware. Most such modems are internal or external USB, but this is not always the case.
Modems can be attached via USB, a traditional serial port, or an internal card slot. Internal and USB modems are more easily autodetected by the operating system and less likely to have problems with setup. USB and serial port modems often require an extra power supply block.
Gaming modems are normal modems that default to having a low compression setting to reduce lag, but are generally no longer used by gamers, who prefer broadband connections.
An ethernet card is required in order to connect to a local area network or a cable or DSL modem. These typically come in speeds of 10Mbps, 100Mbps, or 1000Mbps (gigabit); these are designated as 10Mbps, 10/100Mbps, or 10/100/1000Mbps products. The 10/100 and 10/100/1000 parts are most commonly in use today. In many cases, one or two ethernet adaptors will be built into a motherboard. If there are none, you will have to purchase one - these typically are inserted into a PCI slot. For 10/100/1000Mbps ethernet, it is recomended that you use the adaptor built into your motherboard.
Your computer and you interact through the peripherals. The keyboard and monitor are pretty much the barest minimum you can go with and still be able to interact with your computer. Your choice in peripherals very much depends on personal preference and the complexity of the interactions you intend to have with your computer.
Keyboard and mouse
When choosing a mouse, there is generally no reason not to choose an optical mouse. They are considerably lighter (and as such, reduce RSI) as they have no moving parts, they are much better at smoothly tracking movement, and they don’t require constant cleaning like ball mice (though it may be wise to brush off the lens with a q-tip or other soft tool on occasion). Make sure that you spend money on a decent-quality mouse made by companies such as Microsoft or Logitech, as lower-end optical mice will skip if moved too fast. Mice of medium-to-high quality will track the movement almost flawlessly.
Although three buttons are generally enough for operating a computer in normal circumstances, extra buttons can come in handy, as you can add set actions to extra buttons, and they can come in handy for playing various video games. One thing to note is that with some mice those extra buttons are not actually seen by the computer itself as extra buttons and will not work properly in games. These buttons use software provided by the manufacturer to function. However, it is sometimes possible to configure the software to map the button to act like a certain keyboard key so that it will be possible to use it in games in this manner.
Wireless keyboards and mice do not have a very noticeable delay like they once did, and now also have considerably improved battery life. However, gamers may still want to avoid wireless input devices because the very slight delay may impact gaming activities, though some of the higher end models have less troubles with this. The extra weight of the batteries can also be an inconvenience.
Printer and scanner
For most purposes, a mid-range Inkjet Printer will be more than enough for most people, and you will generally want one that is capable of printing around 4800dpi, and you will also want it to be able to print out fairly quickly. When choosing a printer, always check how much new cartridges cost, as replacement cartridges can often outweigh the actual printer's cost in less than a year. Of course, double check extra information about the printer you are interested in (for example, Epson has protection measures that make refilling your own ink cartridges more difficult because the printer will not see the cartridge as full once it is used up).
For office users that plan to do quite a bit of black and white printing buying a black and white laser printer is now an affordable option, and the savings and speed can quickly add up for home office users printing more than 500 pages a month.
Scanners are useful, especially in office settings, they can function with your printer as a photocopier, and with software can also interact with your modem to send Faxes. When purchasing a Scanner, check to see how "accessible" it is (does it have one-touch buttons), and check how good the scanning quality is, before you leave the store if possible.
Finally, "Multi-Function Centres" are often a cost-effective solution to purchasing both, as they take up only one port on your computer, and one power point, but remember that they can be a liability, since if one component breaks down, both will need to be replaced.
When choosing a display for your computer, you have two key choices of technology: the Cathode Ray Tube (CRT) screen, or an LCD screen. Both technologies have their advantages and disadvantages: CRTs are generally preferred by gamers and graphic artists, for both the price at which they can be bought and their generally superior response times, but this is offset by the added size and weight that a large screen requires. LCDs are generally more expensive than CRTs, but high-end models are generally preferred for tasks which need higher definition, such as movie editing, and are also popular amongst people with little-to-no desk space, as they do not need as much space as a similarly-sized CRT.
Liquid Crystal Displays (LCD's) have the advantage of being a completely digital setup, when used with the DVI-D digital connector. When running at the screen's native resolution, this can result in the most stable and sharp image available on current monitors. Many LCD panel displays are sold with an analog 15-pin VGA connector or, rarely, with an analog DVI-I connector. Such displays will be a bit fuzzy, and are generally best avoided for a similarly-sized CRT. If you want an LCD displays, be sure to choose a digital setup if you can; however, manufacturers have chosen to use this feature for price differentiation. The prime disadvantage of LCDs is "dead pixels", which are small failing areas on your monitor, which can be very annoying, but generally aren't covered under warranty - this can make purchasing LCD displays a financial risk. LCDs are generally OK for fast-paced gaming, but you should be sure that your screen has a fairly fast response time (of 12 ms or lower) if you want to play fast games. Nearly all flat panels sold today meet this requirement, some by a factor of 3. When picking an LCD, keep in mind that they are designed to display at one resolution only, so, to reap the benefits of your screen, your graphics card must be capable of displaying at that resolution. That in mind, they can display lower resolutions with a black frame around the outside (which means your entire screen isn't filled), or by stretching the image (which leads to much lower quality). Running at a higher resolution than your monitor can handle will either make everything on the screen smaller, at a significant quality drop, or will display only a part of the screen at a time.
CRT (cathode ray tube) displays
The other key type of display is the CRT or Cathode Ray Tube display. While CRT technology is older it often outperforms LCD technology in terms of response times, color reproduction, and brightness levels, although LCD displays are quickly catching up. There are two types of CRT displays, shadow mask and aperture grill. An aperture grill display is brighter and perfectly flat in the vertical direction, but is more fragile and has one or two mostly-unnoticeable thin black lines (support wires) running across the screen. CRTs are generally 2-4 times as deep as similarly-sized LCDs, and can weigh around 10 times as much, but this normally isn't a concern unless you will be moving your computer a lot. If you purchase a CRT display over the internet, shipping is much quicker, which is good for gaming, however, can cause headaches in some people at lower rates, so it may be ideal to pick a screen offering higher update frequencies at whichever resolutions you intend to use. Most people who have problems with low frequencies (60Hz) find it preferable to have at least 80Hz at the intended resolution. Some won't be bothered by this at all however.
Note that sometimes the CRTs with a flat screen instead of curved are called "flat screens" so this is not to be confused with the term "flat panel" used to refer to LCDs.
Computer speaker sets come in two general varieties; 2/2.1 sets(over a wide range of quality), and "surround", "theater", or "gaming" with four or more speakers, which tend to be significantly more expensive. Low-end speakers usually suffer from low bass response or having no amplification, both of which make a huge difference in sound. Powered speakers with separate sub-woofers usually cost only a few dollars more and make a significant difference. At the higher end, one should start to see features like standard audio cables (instead of manufacturer-specific ones), built in DACs, and a separate control box. The surround sets are usually identical to the 2.1 set of a manufacturer, just with more speakers, which can be useful for gaming or movie watching. 5.1 and 7.1 support are becoming standard now, however, it is still necessary that you ensure your sound hardware is capable of 5.1/7.1 before buying a speaker system for this. If you have a lot of money you want to spend on audio, it may be wiser to avoid the computer speaker market entirely and look into piecing together a set of higher-end parts. The computer speaker market tends to start pumping up wattage without making any quality improvement - you can usually get more volume, that's all. If you are buying a speaker system designed for PCs, research the systems beforehand so you can be certain of getting one that promises clarity rather than just simple wattage. (Note: speaker power is usually measured in RMS Watts. However, some cheap speakers use a different measure, PMPO which appears much higher.)
Headphones can offer good sound much more cheaply than speakers, so if you are on a limited budget but want maximum quality they should be considered first. There are even headphones which promise surround-sound, though opinions on this are usually not good.