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Following confusion surrounding its Windows x64 Advancement Program, which offers a free upgrade from the standard 32-bit version of Windows XP to the recent 64-bit release, Microsoft has clarified the language on its Web site. All users, whether they purchased or built their PCs, are now eligible for the 64-bit upgrade.

Microsoft previously had said publicly that any Windows XP user with an x64-supported processor, such as an Athlon 64, may trade in their license for the x64 Edition of Windows XP. But the company's Web site for the program said the offer applied only to purchased PCs with an OEM copy of Windows XP.

"Windows XP 64-bit is not gonna be on retail shelves? So how in the world am I supposed to get it," asked on BetaNews reader. "I built a AMD Athlon 64 system for nothing?"

Full story: BetaNews | Windows x64 Advancement Program