Pirates are circulating a hack that lets them activate counterfeit copies of Windows Vista using a spoofed server that Microsoft relies on to make sure enterprises switch on the new operating system.

The software, loaded with the long name of "Microsoft.Windows.Vista.Local.Activation.Server-MelindaGates" is available on several pirate Web sites. It spoofs a Key Management Service server, one of the two technologies that Microsoft debuted last month that let businesses activate a large number of copies of Windows Vista. KMS requires that at least 25 PCs be connected to a corporation's network.

Vista is the first version of Windows that Microsoft requires volume license customers to activate. Besides KMS, the Redmond, Wash. developer also offers Multiple Activation Key, which resembles the retail version's activation process. PCs activated using KMS must reactivate at least once every six months.

The MelindaGates hack uses a VMware image of a KMS server to activate -- and keep activated -- a pirated edition of Windows Vista Business. "Looks like Windows Vista Volume Activation 2.0 is a big bust," wrote a user identified as "clank" on the PirateBay Web site Friday.

Like every edition of Windows, Vista has been plagued with counterfeit copies. Pirated editions with cracked activation keys were posted long before Microsoft officially launched the OS Nov. 30.

However, the Redmond, Wash. developer has gone to greater lengths to stymie counterfeiting, including the overall effort it's dubbed "VA 2.0" for Volume Activation 2.0, which uses a new set of technologies to activate and validate Vista and essentially turn off faux copies.