You may be prompted to activate Windows Vista on a computer on which Windows Vista activation was not previously required. For example, this problem may occur on a computer where Windows Vista was preinstalled by an OEM or by using a Volume Licensing installation. The problem does not occur on Retail versions of Windows Vista. For example, the problem does not occur if you purchased Windows Vista and installed the operating system on a computer yourself.
Although this problem rarely occurs, it may occur during typical use of a Windows Vista-based computer.