Choosing an Operating SystemEdit
This isn't as big a deal for most users as choosing a processor or video card. However, it is an important choice, even if it's just the choice between 32-bit and 64-bit versions. A carefully chosen OS can help to make the entire computer run more smoothly, and can also hel you to take advantage of the hardware in it.
Currently, for the vast majority of computer users, Microsoft's Windows operating system is the system of choice. It comes preinstalled on virtually every non-Apple OEM computer, and many people that build their own computers choose Windows as well. It has the largest library of compatible applications and games as well. If you're building a computer to play games on, chances are that it's going to be a Windows-based system.
The current version of Windows is Windows 7. This version of the OS lauched in mid-2009, and has steadily inscreased in market share, finally overaking the venerable Windows XP in late 2011.
Linux is another option for an operating system, though most Linux users tend to be more computer-literate. Linux is unique in that it is an Open Source operating system. This means that the end user can rewrite the code that forms the basis of how the OS operates. Granted, it takes a great deal of skill to do this, but the ability is there. The accessibility of the source code means that Linus is widely considered to be the most secure option available. The server and database industry, as well as the vast majority of supercomputers run forms of Linux. In fact, the 2009 hit movie Avatar was rendered on computers running Linux.
Linux comes in many different versions, called distributions. The Linuxwebsite maintains a list of the most popular distibutions and also links to their respective websites. The most popular Linux distribution is called Ubuntu.
If you own a PC manufactured by Apple Computer, it came with Mac OSX installed. The current version is actually 10.7, known in the community as Lion. One way in which the Apple OS differs is that the End-User License Agreement stipulates that the software can only be run on hardware manufactured by Apple themselves. Many user get around this by building Hackintoshes, computers that have been altered, either through software or hardware to run the Apple OS. Apple doesn't approve of this practice, and there have been lawsuits against the practice. Needless to say, if you run a Hackintosh, you probably don't want to take it to the Apple Store for help.
Depending on your hardware, your options could be limited as to what you can run efficiently.