If a legitimate copy is not bought within 30 days, the system will curtail functionality much further by restricting users to just the Web browser for an hour at a time, said Thomas Lindeman, Microsoft senior product manager.
Under that scenario, a person could use the browser to surf the Web, access documents on the hard drive or log onto Web-based e-mail. But the user would not be able to directly open documents from the computer desktop or run other programs such as Outlook e-mail software, Lindeman said.
Microsoft said it won't stop a computer running pirated Vista software from working completely, and it will continue to deliver critical security updates.
The company also said it has added more sophisticated technology for monitoring whether a system is pirated. For example, the system will be able to perform some piracy checks internally, without contacting Microsoft, Lindeman said.
Microsoft also is adding ways to more closely monitor for piracy among big corporate users, who tend to buy licenses in bulk.
Microsoft said the upcoming releases of Windows Vista and also Windows Server "Longhorn" will be the first two products to ship with the new anti-piracy measures included.
Windows Vista systems must activate with Microsoft as genuine within 30 days and failure to do so will result in "reduced functionality mode" until successful validation occurs, Microsoft said.
Customers that use genuine versions of Windows Vista will get an enhanced set of features that will not work on non-genuine or unlicensed versions of Vista, it said.
Users of non-genuine Windows Vista software will also be notified by the appearance of a persistent statement in the lower right hand corner of their desktop that reads: "This copy of Windows is not genuine."
The crackdown shows how much more seriously Microsoft has started taking Windows piracy, which for years has been extremely widespread in areas such as Russia and China. The Business Software Alliance, a software industry group, estimates that 35 percent of software installed on PCs worldwide is pirated.
In recent years, the market for Windows - one of Microsoft's main cash cows - has become more saturated. That's left the company eager to make money from users who may otherwise have obtained illegal Windows copies.
Microsoft has already instituted tougher piracy checks for Windows XP users who want to get free add-ons such as anti-spyware programs. But until now, the warnings and punitive measures were mainly seen as annoying, rather than debilitating.
Cori Hartje, director of Microsoft's Genuine Software Initiative, said the company now wants users to notice the difference between legal and pirated copies of Vista.
"Our goal is to really make a differentiated experience for genuine and non-genuine users," Hartje said.
Analyst Roger Kay with Endpoint Technologies Associates noted that Microsoft has the right to curtail illegal distribution of its software. The new piracy measures, he said, "seem harsh only in comparison to how lenient it has been."
Nevertheless, Kay said he expects that the anti-piracy tactics will keep some people from upgrading to Vista from the current operating system, Windows XP.
"There will be an XP backlash, which is to say people (will) cling to XP in order to avoid this," he said.
Kay also doesn't expect the new piracy measures to be that effective against hardcore pirates, who have built de facto businesses selling illegal Windows copies. But he thinks it will stop some lower-level piracy.
After many delays, Redmond-based Microsoft is expected to release Vista to businesses in November and consumers in January.