The Redmond, Washington, company said the legal action is part of renewed effort to stop software piracy of its popular BackOffice and Windows NT Server and Workstation software.
The lawsuits were filed in U.S. District Court in Arizona against the Tucson-based Computers Under Retail and Future Information Design.
The legal action resulted from two undercover operations. In the Future Information Design case, an undercover operation found that the reseller was allegedly installing unauthorized copies of Windows NT Server and Workstation for a customer's network. The lawsuit claims copyright infringement.
Computers Under Retail allegedly sold a counterfeit copy of Windows NT Server to an undercover Microsoft investigator. The reseller is being charged with copyright infringement and trademark infringement.
Future Information Design had previously been issued a cease-and-desist letter, according to Microsoft, after it was found that the reseller was allegedly illegally loading unlicensed copies of software at customer sites.
Customers may email Microsoft to report possible software piracy at email@example.com.