CPU: Also known as the processor, your CPU is often likened to the brains of your machine. It can come in single, dual, triple, or quad-core flavors. Its speed is based in Gigahertz (if yours is measured in megahertz, that’s the first sign you need to upgrade). Simplistically put, the higher the gigahertz, the faster the processor, ie, 2ghz is faster than 1ghz. Once you start getting into the high 2s, however, there is very little difference that can be seen in gaming circles. The two major players in this field are AMD and Intel.
Motherboard: the motherboard is the backbone of your computer, the piece of hardware that all other pieces of hardware connect to. Motherboards come in all shapes, sizes, colors, brands and features so the motherboard is one of the more subjective pieces of hardware around. It is extremely important to note, however, that your motherboard MUST match the ‘chipset,’ or socket, of your processor. AMD motherboards are much easier in this regard as you really only have to worry about socket AM2+ and AM3. Intel motherboards have at least five different sockets, and getting it wrong will mean a machine that won’t even fit together, let alone work.
Memory: Known by its more technical term, RAM is an extremely critical component of the computer environment. Having enough RAM is important, but also make sure it is fast and reliable.
Hard-Drive(HDD or SSD): Hard drives come in many sizes, brands, and formats. It used to be that IDE was the standard format for hooking your HDD to your motherboard, but nowadays SATA2, or SATA 3gb/s, is the new standard (a faster one is still being phased in, although they are harder to find). Most HDDs have a rotation speed of 7500rpms, but can go to 10,000rpms or even 15,000. HDDs are also measure in read speed, write speed, continuous read/write, and random access. These all mean different things at different times and if you want a more thorough explanation, PM me. SSDs are the new breed of hard-drives that do not have discs but are, in effect, giant flash drives. They are hideously expensive for their gigabyte capacity, but extremely fast in all but continuous read/write mode.
Graphics Card: also known as the GPU, the graphics card is the portal to your monitor; without one your monitor won’t receive a signal. Some motherboards have onboard graphics cards, but these are usually not desirable in a gaming situation. The big players in this arena are ATi, which is now part of AMD, and nVidia. The cost and size of the graphics card depends very much on which games you plan to purchase.
Power Supply: This is the beast that provides the juice your machine needs to run. Watts and brands also vary, but for a gaming machine, 500watts can be considered the minimum anymore.
Case: This is the other beast of the setup, and excluding the power supply, the heaviest one of the bunch. As long as it is large enough to fit all of your components there is an endless variety of cases for sale, in every price range.