The company plans to cut off OEMs' XP downgrade rights six months after Windows 7 debuts, limiting computer makers to offering Vista-powered PCs.
"Microsoft has never had this sort of limited time for downgrades, and we think it's going to be a real mess," said Michael Silver, an analyst with Gartner.
The set-up is similar to the one used for Vista, which could be downgraded to XP Professional only from Vista Business and Vista Ultimate. (Vista Business is the closest edition to the upcoming Windows 7 Professional in its feature set.)
Silver outlined the Catch 22 as he sees it. "For an organisation that's trying to skip Vista, that means they really need to buy new PCs that they need to run on XP, and want to upgrade later to Windows 7, by April 21, 2010," he said.
"[But] since a lot of organisations won't be ready for Windows 7 until later in 2010 or even early 2011, any PCs they buy from April 22, 2010 on, and until they are ready to deploy Windows 7, would need an upgrade licence or Software Assurance (SA) to allow them to run Windows XP temporarily, and upgrade to Windows 7 later on."
Corporations that subscribe to SA - Microsoft's upgrade guarantee programme - or purchase Windows through volume licensing plans have downgrade rights from any edition, including Windows 7, to any previous version going as far back as Windows 95.
Silver's scenario means that companies who want to later upgrade new PCs to Windows 7, but want to run XP for the moment - most likely, to keep them in sync with the rest of the firm - will have to buy those machines before the end of April 2010, or purchase SA, or fork over money for an upgrade license from XP to Windows 7 later.
Lacking an SA plan, companies that buy PCs after the 2010 downgrade cut-off would have to make do with Vista or move all the way to Windows 7 if they wanted to avoid a multiple license hit. Neither operating system would be of help if the firm was still standardised on XP.
The alternative to SA: Buy the new PC with Windows 7, then wipe the drive and install a full licensed copy of XP. Later, when that machine is ready to be upgraded to Windows 7, the user would have to buy another license, this time an upgrade to Windows 7 from XP.
Silver saw other problems looming because of the unusual cut-off. "Most organisations are challenged when it comes to asset management anyway, so trying to figure out which PCs need SA or upgrades and which don't could be a challenge, not to mention the additional cash those upgrades will cost," he said.
Microsoft was unable to confirm the details that Silver spelled out about Windows 7's limited-time downgrades.