Microsoft will restrict Windows 7 "upgrade rights" for Vista and XP users to 25 machines at any single street address, meaning that larger companies will have to go through volume licensing for their migration plans, according to a Web site chronicling the rollout of the forthcoming operating system..

Larger companies will have to rely on their Software Assurance (SA) maintenance contracts as the foundation for their upgrade path, but those without SA won't get any upgrade break at all beyond the first 25 PCs. SA gives users rights to upgrade to new versions of any software they have under their SA maintenance contract.

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