Microsoft has released a revamped version of its WGA (Windows Genuine Advantage) tool that it hopes will reduce complaints from paid-up users of Windows XP.

The new approach to WGA Notifications introduces a category of results for PCs with Windows installations of questionable validity. This aims to address complaints from users who have yet to pass WGA by creating an "indeterminate" category for copies of XP that failed to prove they were genuine yet didn't use a licence of XP known by Microsoft to be pirated.

Users with copies of XP labelled "indeterminate" are also provided with more information to troubleshoot the problem, according to a Microsoft spokeswoman.

The change addresses a problem raised by the other half of Microsoft's antipiracy program, WGA Validation, which was introduced in mid-2005. PCs that were scanned by WGA Validation and failed to prove to Microsoft’s satisfaction that they were running non-counterfeit copies of Windows XP were formerly labelled as "non-genuine" by Microsoft.

That caused WGA Validation to disallow access to certain Microsoft software, and WGA Notifications to send periodic messages asking users to reinstall XP or buy a legitimate licence for it, leading to "nagware" complaints from some users.

Many users also claimed that WGA, due to technical glitches or other issues, mislabelled their genuine copies of Windows XP as pirated. Microsoft has maintained throughout that the rates of such "false positive" errors were very low.

At the same time, its online forum for WGA-related problems has registered nearly 20,000 postings from aggrieved users.

Microsoft keeps a database of pirated XP licences, most of which are stolen from corporations using a single volume licence to install multiple Windows on multiple PCs.

The majority of Windows XP users, whose copies of XP have already passed Microsoft's WGA program, can safely ignore the updated tool.

Users running copies of XP that Microsoft has already determined to rely on one of four pirated Windows licence keys are now being asked to download the revamped tool. That will be gradually expanded over the "next several weeks and months", according to Microsoft, though users will continue to be able to de-select the update from being downloaded and installed.

The new version of WGA Notifications will not incorporate a "kill switch" that cripples PCs that fail to prove that they’re running genuine copies of Windows XP. That more aggressive feature, called RFM (Reduced Functionality Mode), is being introduced in the upcoming Windows Vista OS.

The release also features a new installation wizard and will display validation results as soon as the tool has been installed. The software doesn't need to be rebooted after its installation, Microsoft said.

Microsoft plans to update the tool every 90 to 120 days, as a way to react to re-evaluation of the software and any changes in software piracy.