Attempting to stay a step ahead of software counterfeiters, Microsoft this month plans to release an update for Windows 7 that will scan computers for evidence of the latest tricks being used by tech pirates to fool the company's software-activation technologies into thinking counterfeit operating systems are the real thing.

As in the past, the channels of distribution will include the operating system's Automatic Update mechanism. That practice has gotten Microsoft in hot water in the past -- including a recently dismissed lawsuit that accused the company of using its security-update pipeline to quietly distribute what amounted to spyware.

However, the company is making the update voluntary this time, and it's making a point of announcing it publicly in advance. In addition, if the new check determines a user's Windows 7 copy to be pirated, the repercussions are less severe. Windows no longer removes access to features in those cases, but instead turns the background black and takes other steps that essentially amount to nagging.

"Over time, we have changed our approach, mostly based on customer feedback," said Joe Williams, general manager of Microsoft's Genuine Windows initiative, in an interview. "We’re just a lot more open and transparent about what our business methods are."

Williams announced the plan in a blog post this morning. It's the latest step in the company's long-running effort to cut down on piracy and boost sales of genuine Windows copies. Microsoft also says it's trying to protect customers, citing studies showing that pirated systems can come chock full of traditional spyware and other malicious code.

In the interview, Williams said the company says doesn't collect "personally identifiable information" from computers as part of the anti-piracy scan. However, as noted in this privacy policy, the company does collect, temporarily, the IP address associated with a machine. One of the most interesting aspects of the recent court case was the judge's ruling that IP addresses didn't qualify as personally identifiable information.

"We do collect the IP address. We do not keep it," Williams said. "Where we have a machine-specific item, we convert that to a hash, so we don't keep the particular item. But it helps us to understand when that unique PC visits us or revisits us."

The new update will scan systems for two tactics being used by counterfeiters to trick the company's Windows Activation Technologies into thinking pirated systems are genuine -- manipulation of registry settings, and a modified "bootloader" that intervenes when the operating system is loading.

The company plans to make the update available for download from its website starting Feb. 16. Later in the month, the update will be available through the Windows Update system as an "important" update (as opposed to the higher ranking of "critical"), which means that people who have their Windows 7 machines set to receive those updates will receive them automatically as if they were getting a security patch. The update will also be uninstallable if a user finds out later and wants to remove it.

After installation of the update, the system will check back with Microsoft's server ever 90 days for further updates, and if they're available, it will scan the system again to see if it has been pirated.

"For most Windows users in the developed world its impact will be nonexistent; on a system with a properly activated copy of Windows, it will make an initial validation check, update itself every 90 days, and never make a peep," writes Ed Bott, an independent Windows author and blogger, in a post today. "What’s noteworthy to me is the degree to which Microsoft is going out of its way to disclose the details of this update and to allow anyone who is skeptical of it to opt out with no negative consequences."

People whose systems are determined to be pirated will be given an opportunity to buy a genuine Windows copy at a discounted rate. There will be deeper discount if they help Microsoft identify the source of the counterfeit, Williams said.

At the same time, people who continue to run systems identified as pirated won't be able to use free software from Microsoft, such as its Microsoft Security Essentials program.

But why bother distributing an update such as this as voluntary? Won't people who know they're running pirated copies just skip it? The answer is yes, but the company says it believes many people who bought pirated systems from questionable sources have been tricked into thinking they're running a real copy, particularly as counterfeiters get better at making high-quality installation discs.

More coverage: Paul Thurrott, Mary Jo Foley, and Ina Fried

Post updated at 10:30 a.m. with additional information.