Unlike Windows XP, which was sent barefoot into the world, Windows Vista comes in the context of a mature anti-piracy infrastructure courtesy of the Windows Genuine Advantage mechanism, and with the Reduced Functionality Mode limitations. Reduced Functionality Mode in Vista is delivered in two distinct flavors: out-of-grace and non-genuine. The first is associated with operating systems that have not been activated in the initial 30
days grace period while the second is a result of the detection of a potentially pirated copy of the platform.
"Windows Vista may enter reduced functionality mode if one of the following conditions is true: you do not activate Windows Vista within the specified activation period; you modify the computer hardware so that Windows Vista determines that it is running on a different computer. Also, you do not activate Windows Vista within the grace period for reactivation. For retail Windows Vista products or for original equipment manufacturer (OEM) Windows Vista products, this reactivation grace period is three days. For volume licensed Windows Vista products, this reactivation grace period is 30 days, and you are running a version of Windows Vista that the Windows Genuine Advantage (WGA) service detects as a "non-genuine" version of Windows Vista," Microsoft informed.
Retail copies of Vista can move into Reduced Functionality Mode if the operating system was not activated within the first 30 days of the installation, or within three days of a major hardware change. OEM versions of the platform require re-activation within three days of swapping the motherboard for a non-OEM motherboard. The corporate and enterprise versions of Vista will continue to function normally for a total of 30 days after a hardware upgrade, and following the initial installation. These details are valid for Vista copies using both the Key Manager Service and the Multiple Activation Key. The only difference is that Vista will have to access a KMS server no longer than 210 days after the original activation or it will move to Reduced Functionality Mode.
"Windows Vista enters non-genuine reduced functionality mode if one of the following conditions is true: the WGA program detects a blocked product key or a counterfeit product key; the WGA program detects incorrect activation binary files or modified activation binary files and Windows Vista is in out-of-grace reduced functionality mode," Microsoft added.