Three of the top four PC sellers worldwide plan to sell systems with Windows XP right up to the Microsoft-mandated deadline of June 30.

Of the four, only Dell plans to call it quits before the last day of this month.

Microsoft has set June 30 as the final day of Windows XP availability to retailers and major computer makers, although the company recently also said that the date won't mark a sudden disappearance of the old operating system.

"The exact cut-off day for selling Windows XP is determined by OEMs and retailers, who can keep selling standalone versions as well as PCs with Windows XP preloaded by OEMs distributed prior to June 30, 2008, as long as their supplies last [emphasis in original]," a Microsoft spokeswoman said two weeks ago in an e-mail.

Hewlett-Packard, Acer, and Lenovo -- ranked nos. one, three and four, respectively, in global PC sales in the first quarter by both Gartner and IDC -- will continue to sell XP-powered machines until June 30, the companies said this week in response to questions from Computerworld . Dell, which is the world's number two OEM, is sticking to June 18 as the last day that customers can order computers with XP pre-installed.

Here's what the OEMs said about their plans:

Hewlett-Packard: "We do still offer XP on a select number of our existing consumer notebook, gaming and business products," said a spokesman for HP. "This will continue through the XP end of life date on June 30, 2008."

Dell: Weeks ago, Dell said that it would stop taking customers' orders for PCs with XP after June 18. Wednesday, an e-mail from Dell's small business group titled "Last Chance" repeated that date. "It's time to decide if you want a Dell system with pre-installed Windows XP or Windows Vista," Dell's marketing e-mail read.

Acer: "For Acer, it's June 30," said a spokeswoman for the Asian OEM's American operations.

Lenovo: Although Lenovo spokesman Doug Bell first said his company's last-sale date was June 15, after checking, he confirmed that it is, in fact, the end-of-life June 30.

Some of these computer makers, however, will continue to sell PCs with factory-installed XP licenses after June 30 by taking advantage of Windows Vista's downgrade rights.

A clause in Microsoft's guidelines for OEMs lets computer makers install Windows XP Professional -- but not the more common and less expensive Windows XP Home -- on new PCs at a customer's request when those machines are ordered with Windows Vista Business or Windows Vista Ultimate.

Dell was the first to say it would use the downgrade clause to offer buyers XP Professional pre-installed long after the June 30 deadline. Those PCs will also include Vista installation media so that customers can, if and when they want, upgrade from XP. Dell, however, has not said how long it would offer the downgrade option.

Not so with HP. "HP has been offering business desktops, notebooks and workstations with the option to downgrade to Windows XP Pro from Vista since August 2007, and will continue to offer this option on its business systems through at least July 30, 2009," said the HP spokesman.

Lenovo, meanwhile, said it would continue to offer its downgrade option -- Lenovo doesn't swap out the Vista for XP at the factory floor, but instead sends media that requires the user to re-install Windows XP -- until Jan. 31, 2009.

Make no mistake about it, June 30, 2008 is the beginning of the end for Windows XP, even with Service Pack 3 available for two months now, since May 6.

Microsoft confirmed that the end of this month will be synonymous with the availability cut-off date through the retail and OEM channels, although there have been customers hoping until the last minute that the company would breathe new life into the predecessor of Windows Vista.

Microsoft has already postponed once the availability end date initially planned for January 30, 2008, but the company was firm on the fact that that was an exception which would not be repeating itself.

"In industry speak, this is called "end-of-sales." On June 30, Microsoft will stop distributing Windows XP as a stand-alone product that you can buy shrink-wrapped in the store. We'll also stop sending it to Dell, HP, Lenovo and all the other major PC manufacturers to sell on their PCs. That said, Windows XP isn't going to disappear overnight", revealed Mthree Sweatt, Chief of Staff of the Windows Core Operating System Division (COSD) at Microsoft citing the new The Facts About the Future – Windows XP website.

Microsoft argued the need to sacrifice Windows XP on the altar of innovation and to continue focusing entirely on Window Vista. The company stressed the fact that it would not be pulling the plug on the operating system, which would continue to benefit from extended support until 2014. Mainstream support will be retired in April 2009, while Extended support will be killed in April 2014.

"You may still see copies of the software—or computers pre-loaded with it—for months, as stores and PC makers work through their inventory. Also, smaller local PC makers—known in the industry as "system builders"—can continue to sell PCs with Windows XP until January 2009. Finally, Microsoft recently announced that computers with limited hardware capabilities—devices sometimes called Netbooks or ultra-low cost PCs (ULCPC)—can carry Windows XP Home until June 2010", Sweatt added.

The Windows XP era ends June 30 and soon hardware vendors will be shipping you all Vista all the time (in most cases).

The save XP effort failed. The whining should cease. And now it’s time for Vista to sink or swim.

Ina Fried has a good overview of where Windows XP will stand with PC manufacturers. And Matt Asay highlights a report from Evans Data noting that 92 percent of developers are ignoring Vista. Coupling these two items together and you come to one conclusion: Folks are skeptical about Vista, but a lot of that skepticism is because XP is still lingering.

If you’re a Vista complainer you have two options from here:

* Move away from Windows completely (users try a new OS and developers jump ship).
* Or shut up and go with Vista.

My hunch is most folks will do that latter. I’d love to believe that Microsoft’s Vista miscues would result in a mass exodus, but I doubt that will happen. I also wonder why people live in New Jersey and pay those ridiculous property taxes, but shockingly enough people stay. Based on my Libertarian leanings I’d reckon there would be four people left in Jersey by now.

But I digress. Once consumers no longer have the XP option they’ll fall in line with Vista. Sure some percentage will go Mac, but if you didn’t jump yet–after a gazillion brilliant Apple ads knocking Vista–you probably won’t. And the developer worries: Developers will fall in line too. Evans Data notes:

Only eight percent of North American software developers are currently writing applications to run on Microsoft’s Vista operating system, while half are still writing programs for XP, according to Evans Data’s Spring 2008, North American Development Survey. These same developers forecast a fragmented Windows market in 2009 with only 24 percent expecting to target Vista and 29% expecting to continue with XP.

“Developers have taken a wait and see approach to Vista”, said John Andrews, Evans Data’s President and CEO. “The new operating system has had more than its share of problems and the desire to move from XP on the Windows platform is still lagging - that coupled with interest in alternative operating systems is suppressing development activity and that in turn will further erode Vista’s acceptance.”