UNeconomic.
Two problems with it:
1. It's XP Professional. Unless you specifically know for a fact that you need the extra features in Professional, skip it. Go for Home Edition (the green box.)
2. It's an 'UPGRADE' version. This means that in order to install it (it does check,) you have to have an existing copy of Windows on your computer. This will *NOT* install into either Parallels or Boot Camp.
What you want is to buy Windows XP Home 'Full Retail' edition. (Also marketed as "For PCs without Windows, or PCs with Windows 95 or earlier versions.") This has a 'retail' price of about $199.
Costo has it for $189.99, but you can find it from many online retailers more cheaply.
Also available are 'OEM' copies. With a 'full retail' copy, or even an 'upgrade' copy, Microsoft is selling you the full product, as well as the right to technical support direct from Microsoft. An 'OEM' copy is a copy that is meant to be sold along with a computer. This is what Dell, HP, Gateway, etc, all do. The OEM copy means that the computer manufacturer is responsible for giving you the disc, manual, and all technical support. With big companies, they actually do all of that. For smaller 'mom and pop' type shops, they buy a small shrinkwrapped 'manual+CD' combo from Microsoft that is meant to only be sold with new computers. But, some stores will sell one without a computer, or when buying ANY piece of computer hardware (one online seller includes an old horribly obsolete (and likely nonfunctional) processor, so that they can claim that they are following the letter of the license.) These can be found online as cheaply as $30, if you're willing to 'fudge' the intent of the license a little. (The OEM license specifically states that you must use the copy of Windows on the computer that the copy of Windows shipped with. If you buy it with just one component of a computer, you must use that component with the computer. So if you bought it with the horribly obsolete processor, there is no possible way you will be using that processor with the copy of Windows, making it a license violation. You *CAN* however, buy it with a mouse, and if you use that mouse with the computer, you would technically be following the license.)