Why do we use the "QWERTY" keyboard? Why not have the keys laid out in alphabetical order?
On August 27, 1878, Christopher Latham Sholes put forward patent number 207559, for "The Type X W Writer". The name 'QWERTY' comes from the first six keys which are on the top left of the keyboard that we still use today in computing.
The original layout of the typewriter keyboard was different than what we are using now, but was changed due to a problem with the typebars hitting each other and getting stuck, jamming the platens together. If you have ever used an old-fashioned "Clackity-Clack" typewriter, you know what I am talking about. The order was changed so that common letter combinations would be spaced apart, reducing the jams.
It wasn't long after people started learning the awkward keyboard layout, that they became used to it and then mastered it. Over the years, many other keyboard layouts were developed and put to the test, but the 'QWERTY' became the Universal standard that we use today, simply due to the fact that generations of people had been brought up on the layout.
The biggest competition to the 'QWERTY' is the "American Simplified Keyboard", patented by Dr. August Dvorak in 1936. Some still argue that it is superior in design, however Dr. Dvorak was unable to get it to catch on with the masses.
The Dvorak keyboard layout can be set on your Windows XP computer simply by going to: Control Panel (Classic view) > Regional and Language Options > Text services and Input languages > Installed services (Add) > and under Keyboard layout/IME, select the keyboard layout you want. You may need to reboot your computer for it to take effect. Detailed instructions for doing this can be found at: http://www.microsoft.com/enable/training/windowsxp/keyboardlayout.aspx
With some scripting modification, and a little know-how, it is easily possible to customize and remap the configuration of your computer keyboard to whatever you want the letters to be on keypress, or even allow you to type one handed, holding down the spacebar or other modifier key to toggle the letters.
You can also purchase specially designed keyboards with alternative layouts. These are typically purchased by people that need modifications for accessibly due to a special need, or by gamers who want to program hot keys to do certain functions, such as for flight simulators. Even with all these alternatives available, it seems that 'QWERTY' is here to stay, even though the original reason for the layout is obsolete.