A bug has been reported (and addressed by this hotfix) whereby you may be prompted to activate Windows Vista on a computer on which Windows Vista activation was not previously required. An example of this is if you get Vista installed by an OEM or using a volume license. This specific issue does not occur on Retail versions of Windows Vista (if you installed it yourself).

It can happen if a specific system setting is removed when a program runs with administrative credentials. Of couse they don't tell you what that is, but the removal of this system setting may cause a BIOS validation check to fail. The BIOS validation check is part of the system activation process. Therefore, you may be prompted to activate Windows Vista, even though the system did not previously require activation.

They do provide a specific example where this problem is known to occur when you use Intuit QuickBooks 2007 (although it is not necessarilly limited to QuickBooks and can happen if you installsome "other programs or device drivers". No, don't go yelling at Intuit! Microsoft admits that this is not an issue in the installed program or device driver, but is caused by a system problem in Windows Vista.