Processor

• The processor is the computer's brain, and it coordinates what happens inside your computer. Processors have become more complicated in recent years, with multi-core processors becoming more widespread. Some modern games prefer, or even require, a dual-core processor, which consists of two processors acting in tandem.
  
  The basic measurement of processor speed in modern computers is gigahertz, or GHz. The more GHz a processor has, the more rapidly it can run your game. However, if they have the same amount of GHz, a dual-core processor will run faster than a single-core processor. For example, The Sims 3 can run comfortably with a 2.6 GHz single-core processor, but only requires 1.8 GHz for a dual-core processor.
  
  

Memory

• Your computer's memory, or RAM (Random Access Memory), is responsible for storing all the information that your computer is using at the moment. The more RAM your computer has, the more information it can keep on hand at the same time and the more it can do at once. While The Sims 3, for example, only requires 1 GB of RAM, having more RAM will help the game run smoothly and quickly.
  
  Having more RAM will also allow you to run more than one program at once. While The Sims 3 will run fine with 1 GB of RAM, with 2 GB of RAM you can run the game without having to close down other programs you have running in the background, such as an MP3 player or web browser.
  
  

Video Card

• This card is in charge of managing all the visual elements of the game you're playing. A more powerful video card not only means higher-quality images, but also faster frame rates and less slow-down. For example, while a slower card may be able to run your game fine when there are four characters on screen at once, it may slow down or even stop working altogether when there are 12 characters on screen.
  
  The basic metric for video card speed is how much memory they have. Also, many games require the use of specific brands of card. For example, The Sims 3 for Windows requires a card with at least 128 MB of RAM and only supports NVIDIA GeForce or ATI Radeon cards.
  
  

Hard Drive

• The hard drive doesn't have much effect on how fast games will run on your system, but it does affect how many games you can keep stored on your computer. While, for example, The Sims 3 only requires around 7.1 GB of free hard drive space, you'll need a lot more than 7.1 GB if you want to install other games and download music or movies.
  
  A large hard drive is a good addition to a gaming computer. But if it isn't in the budget, you always have the option of uninstalling a game when you're done playing it and re-installing it later, so that it doesn't take up too much free space.