According to James Bannan over at APC Magazine, even a simple device driver update could result in an installation of Windows Vista to be deactivated. This could be especially problematic on an overseas business trip, as Vista is bumped back into reduced functionality mode when it fails to activate within three days.
When the machine is first activated, Windows establishes a baseline based on the installed hardware, but interestingly the information is not gathered from hardware IDs (which are not necessarily unique), but from hardware information as reported by device drivers. Any changes away from this baseline are weighted depending on the change (for example, a new CPU counts much higher than new RAM) and once the baseline threshold is passed, Windows deactivates and a new activation request is generated.
The issue has to do with how Windows uses device drivers as the basis for the activation information, since device drivers can and do get upgraded over time. In such a case, the hardware information could be reported back to Windows as a physical hardware change.
So what this essentially means is that keeping your drivers up-to-date is a potentially very risky process, with all changes monitored and changes weighted cumulatively.
James concluded that legitimate purchases are unfairly penalized and are left to live with Windows Activation. Pirates, on the other hand, will probably apply an official workaround available for OEMs and get a fully-functional pirated copy of Vista Ultimate that does not require activation — or even a product key.
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