SEATTLE — Microsoft Corp. is pulling back from a system that disables programs on users' computers if it suspects the software is pirated, opting instead for a gentler approach based on nagging alerts.

Microsoft said late yesterday it will roll out the new version of Windows Genuine Advantage with the first "service pack" for Windows Vista, due in the first quarter of 2008.

When computer users activate a copy of Windows Vista or try to download certain software from Microsoft's Web site, the Windows Genuine Advantage system scans their PCs for signs of pirated software. Today, if the tool finds an unauthorized copy of Vista, the glassy Vista user experience disappears and other features are suspended.

In the new version, PC users found to have a pirated copy of Vista will continue to be able to use their computers, but with unmistakable signs their operating system is a fake. The desktop wallpaper will turn black, and a white notice will appear alerting users to the problem. Each time they log in, they will be prompted to buy legitimate software, and every hour, a reminder bubble will appear on the screen.

Users with a high tolerance for irritation can put off switching to genuine software indefinitely, but those who relent and buy a real copy of Windows can do so at reduced prices — $119 for Windows Vista Home Premium, half the regular retail price.

"We want to make sure unwitting victims get a great treatment," said Mike Sievert, a corporate vice president in Microsoft's Windows marketing group.

Windows Genuine Advantage collects several pieces of information about a PC during the check, including the serial number on the hard drive and its IP address, but Sievert says none of that can be used to identify individual PC users.

In August, the Windows Genuine Advantage team at Microsoft accidentally updated its servers with computer code that wasn't quite ready for prime time. As a result, Microsoft said "fewer than 12,000" people who tried to validate software over a two-day period couldn't.

Some found legitimate copies of Windows hobbled after the tool labeled them pirated, and an outcry spread across Web forums and technology news sites.

Sievert said the glitch in August was unrelated to the change in how the Windows Genuine Advantage tool will work.

"Microsoft realizes it has to take a different approach with their customers," said Chris Swenson, a software industry analyst for market researcher NPD Group. "If you shut down someone's computer, you're going to anger customers."

Microsoft also said yesterday the package of Vista updates will fix two holes in the operating system that have allowed pirates to create counterfeit copies — one that mimics the activation of software by computer makers before a PC is sold, and one that extends a grace period given to people who install new software, before they must activate it.

Sievert said Microsoft plans to offer an update for Windows Genuine Advantage that will run the piracy check regularly without the computer user initiating the process.