On Friday, Microsoft flipped a virtual switch that made its Office Genuine Advantage (OGA) program mandatory for nearly all Microsoft Office users. Office users who want to download Office add-ons from the Microsoft Web site will now need to pass a software-legitimacy test similar to that of the company's Windows Genuine Advantage (WGA) program. Previously, OGA was voluntary in most markets.

As you might expect, OGA's technologies are based on WGA, a controversial program that occasionally reports that legitimate Windows copies are pirated. WGA is being enhanced in Windows Vista to be even more problematic, but OGA is based on the earlier version of WGA that Microsoft developed for Windows XP.

OGA is invoked when a user with Office 2003 or Office XP navigates to Microsoft's Web site and attempts to download a free update, such as a template. In January, the program will be extended to include non-critical software-update downloads. As with WGA, Microsoft will let all users access critical software updates.

OGA has one interesting benefit: Users who are unknowingly running pirated Office versions will--as with WGA--be provided with information about how to purchase legitimate copies of the software. But users can receive a free legitimate copy of Office under certain circumstances. Microsoft calls this offer the "Genuine Office Complimentary Offer" and said it will be offered only to those users who clearly obtained a "high quality" counterfeit version of the software and could have been duped by a seller. To qualify for this offer, the user will have to fill out a counterfeit report, provide proof of purchase, and send in the counterfeit CDs, Microsoft said.

Users who can't provide this information can pay for a legitimate Office license online. The cost ranges from $139 to $359, depending on the version of the Office suite.