Microsoft has filed lawsuits against seven partners for violations of a partner agreement.
The suits were filed against US companies that obtained software through the Microsoft Action Pack Subscription (Maps) programme that offers discounts on Microsoft products for internal use.
Redmond has alleged that some of the partners used auction websites to sell the software to consumers.
The suits mark the first time that Microsoft is pursuing legal action against Maps partners.
"Our partners are negatively affected by the activities of those who compete unfairly by either selling illegal software and components or abusing agreements that other partners abide by," said John Ball, general manager for Microsoft's US System Builders Partner Group.
"These dishonest resellers sell products at minimal costs, undercutting the business of legitimate resellers. Those who operate ethically within the law take a hard financial hit. We like to see our honest partners succeed."
Microsoft became aware of the fraudulent trading after an internal audit showed that the resellers forged information to receive software more often than the programme provided for.
The software maker also filed three lawsuits against Auction Hut from Toledo, Ohio, Comp-Discounts from Boca Raton, Florida and Computer Techs based in Grove City, Pennsylvania.
The stores are accused of selling counterfeit software. Microsoft warned buyers to stay away from software costing less than the regular price because it could be an illegal copy.
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