Windows XP has risen from the grave so many times, it now has more in common with Friday the 13th's Jason Voorhees than it does with other PC operating systems. Though its successor--Windows Vista--has been on the market for over two years and yet another Windows version, Windows 7, will ship in just months, Microsoft has again extended the time frame for consumers who wish to continue using the seven-year-old XP. This time around, the company is allowing custom PC builders--alternatively called "system builders" and "white box PC makers"--to continue ordering XP for their PCs through May 30, 2009.
The previous deadline was January 31, 2009, so the extension gives custom PC builders an extra four months to get their XP orders in. After that time, they can continue selling PCs with Windows XP only for as long as their XP stock lasts.
First-tier PC makers--companies like Dell, HP, and Sony that buy Windows in vast quantities--had to essentially stop selling XP on June 30, 2008, though these companies can also take advantage of "downgrade" rights to offer XP at extra cost to consumers if desired. This option hasn't proven particularly popular with consumers.
This extension also doesn't apply to netbook manufacturers, who are currently operating under a longer schedule that applies only to Windows XP Home Edition: These systems can ship with the older OS until June 30, 2010, or one year after Windows 7 ships, whichever comes last. (My guess is that those two dates will be identical, actually.)
Windows XP was supposed to sail off into the tech sunset on January 30, 2008, but the emergence of netbooks and other low-end PCs, as well as perceived problems with Windows Vista, have caused unprecedented demand for what would otherwise be considered obsolete technology. Barring any unforeseen circumstances--perhaps a late night visit to a graveyard with a misplaced bolt of lightning--one can reasonably expect XP to finally stumble disappear for good sometime in our lifetimes. Maybe.