It seems that people are really desperate NOT to pay for Windows. It seems that someone who was "just testing his VBScripting skills" has posted a routine that attempts to activate a pirated copy of Windows Vista by brute force. That means that the script increments through methodically generated keys, and attempts to pass it on to Microsoft's activation servers for validation. If it fails, the generator moves on to the next one, until it finds a valid key. The author says this process can take anywhere from 2 hours to two days. Adrian explains how it works here.
Here's the problem with this, folks. Previous Windows cracks have used leaked corporate activations keys to unlock Windows, which only really hurts Microsoft. This method actively steals a valid Product Key from Microsoft customers, because most keys can only be activated once. Think about that for a second. What if your mom just got home from laying down $150 for Windows Vista Home Premium, only to get it home and install it, and find out that their key has already been activated. Now, Microsoft doesn't get hurt, because the key has been paid for.