The approaching death of Windows XP may upset you, but it shouldn't come as a surprise. Microsoft's product lifecycle guidelines have foretold the fate of XP since 2001. In fact, Microsoft has been killing off one version of a product as it is replaced with another for years now. But this time around, the approaching demise of XP is getting more attention than, say, the final passing of Windows 2000.

Why? For a couple of reasons: XP is the most widely used operating system on the planet, and its long-delayed successor, Windows Vista, is not proving to be universally popular. The companies that make up the enterprise market for Windows are dragging their feet about upgrading, and on the consumer side there are signs of a rebellion against Vista.

Microsoft has already made changes in its timetables: Last year, the company extended the sales lifecycle -- the time during which PC manufacturers and system builders could sell computers with XP installed -- to June 30, 2008. It will stop selling XP altogether on January 31, 2009. And it extended the mainstream support period for XP to April 14, 2009 in an effort to reassure customers made nervous by the long delays in shipping Vista.

The result of all this tweaking is that Microsoft will stop selling XP long before it stops supporting it. You may be able to run XP for as long as you want, but before too long you may not be able to buy a legitimate copy of XP to run.

So will there be any way to get a copy of XP after June 30? If you want to continue using XP, what problems will you face? If you buy a PC with Vista installed and decide you want XP instead, what are your options?

The product lifecycle guidelines

Microsoft's product lifecycle guidelines grew out of two sets of needs: Microsoft's need to make a profit, and its customers' (particularly enterprise customers) needs for some certainty about the products they were committing to.

The policy was an attempt at transparency, a promise that new products would be supported for a definite period and that as they aged Microsoft wouldn't just abandon them. Instead, the company would withdraw support in a series of scheduled steps that corresponded to the pace of technological change, allowing customers time to transition to newer products. (The guidelines apply to all Microsoft products, not just operating systems.)

The problem is that what sounds like a promise to some (particularly enterprise customers) can sound like a threat to others -- particularly consumers. And they're not taking it well.

This incipient consumer rebellion is a relatively new phenomenon, even in the short history of personal computers. For most of the '90s, Microsoft couldn't bring out new products fast enough to satisfy customers. Computing technology was exploding, and Windows exploded along with it, from Windows 3.1 to Windows 95 to Windows 98 to Windows 98 Second Edition to Windows Millennium Edition. PC sales boomed and Windows users raced to upgrade to the latest version.

But that binge left Microsoft with a huge hangover. As the new decade started, it was supporting a tangle of versions and upgrades. Then the Internet bubble burst and PC sales slowed. New products like Windows ME weren't as well received as the older ones. Microsoft needed to reduce its support liabilities and create a profit plan. The product lifecycle guidelines were the solution.