"Our network came to screeching halt," said Zander, who eventually fixed the bug by working with Microsoft technical support.

Such complaints, along with two class-action lawsuits, forced Microsoft to pull WGA's most intrusive features and make it optional. Having learned its lesson with WGA, Microsoft is likely to proceed more cautiously with its Office counterpart, which it began testing in April.

"Microsoft has almost no competition with Windows," said Joshua Erdman, president of San Luis Obispo, Calif.-based software reseller Digital Foundation Inc. "With Office, it's a lot easier to switch to something like OpenOffice or StarOffice. So Microsoft can't afford to [anger] people as much."

OGA, for now, consists of an ActiveX-based tool that users are invited to download on a voluntary basis the first time they get certain noncritical updates from Office. Like WGA's validation tool, OGA checks to see whether the license key is stolen or counterfeit. If it isn't, the tool stores a special download key on the PC to aid in future verification.

Adrian W. Kingsley-Hughes, a U.K.-based technology consultant who runs the blog The PC Doctor, said OGA mistook his legal copy of Office for a pirated one. "No idea why I had problems," he said. "I was quite surprised when it said it didn't check out."