The Rasputin of operating systems defies yet another planned death date, as a leaked internal memo from Microsoft makes it clear that Windows XP will continue to live on.

In the memo, Microsoft says it will continue support for Windows XP beyond its latest retirement date of May 30, 2009. Unconfirmed rumors are also circulating that Microsoft will allow Hewlett-Packard to continue shipping computers with Windows XP until April 30, 2010. If that’s true, it’s likely that Microsoft will let other PC vendors do the same.

Perhaps one reason for the extension has to do with the popularity of netbooks, primarily designed for wireless communication and Internet access to Web-based applications. Netbooks typically run some version of the Linux operating system or Windows XP. Microsoft’s Vista is too resource-intensive for the small, low-powered machines.

Despite Windows 7's early popularity, there’s still no confirmed release date, though it’s tentatively scheduled for general availability in October 2009, according to industry sources.

While Microsoft will continue to sell XP, the software giant states in the memo that XP mainstream support will be discontinued, and only security updates will be provided.

"It's important to remind customers that Microsoft are [sic] still planning to retire XP Pro Mainstream support on April 14, 2009 and will only provide OS security updates beyond that date unless the customer has an Extended Hotfix Support contract. MS Extended Support for XP Pro ends on April 8th, 2014," according to the memo.

And it’ll still cost buyers of Windows Vista whose customers want to maintain downgrade rights. While some PC vendors like Dell are charging as much as $150 to downgrade customers from Vista to XP, it’s still unknown how much HP will charge. The downgrades have been used to pacify businesses and consumers that were unhappy with Vista’s compatibility, security and performance woes.

HP was contacted about this report, but has not responded with comment.

Microsoft’s position is that extending XP to and beyond this point allows consumers the choice of upgrading their systems to the “better” Vista (a euphuism for Windows 7) or sticking with Windows XP.

"Based on feedback, Microsoft is further broadening the options provided to direct OEMs to help customers facilitate end-user downgrade rights included in the product license terms of a new system with either Windows Vista Business or Windows Vista Ultimate. These product versions are the only ones to include such end-user downgrade rights,” a Microsoft spokesperson tells Channel Insider.

“This option is designed to help direct OEMs further support customers, primarily small-business customers, looking for Windows XP Professional due to application compatibility concerns.  End-user downgrade rights are a right in the end-user license for Windows Vista Business and Ultimate products, and therefore remain in effect for the life of the product, so this change does not represent an extension,” the spokesperson says. 

Nor does Microsoft plan to further its downgrading habit, the spokesperson says.

“Microsoft does not have a downgrade program. It does offer downgrade rights as part of some Windows Vista licenses, including Windows Vista Business purchased through the OEM channel.  Microsoft does not charge or receive any additional royalty if a customer exercises those rights.  Some customers may choose or need to obtain media or installation services from third parties, such as OEMs, to install the downgrade version,” the spokesperson says, adding that the inclusion of downgrade rights isn’t exclusive to Vista and XP.

“This is not the first time that Microsoft has offered downgrade rights to a version other than its immediate predecessor.  In fact, our Software Assurance customers can always downgrade to any previous version of Windows," the spokesperson says.