OEM copies of Windows are permanently locked to the motherboard after installation, a limitation imposed by Microsoft. Attempting to install it on another system will report the license as invalid when the hardware is checked during activation. Windows XP and Vista also 'phone home' to Microsoft's servers every two weeks or so, as well as every time a 'major' hardware change is detected, to determine if it is still valid on that machine. Thus, even if Microsoft verifies that the key is valid the system may say it isn't because the key is registered for another hardware configuration. While BIOS upgrades and drivers don't usually trigger the alarm, so to speak, it can happen, particularly with a manufacturer's customized version of Windows during the installation process.
P.S. You'll be happy to know that Vista SP1, due out next month, removes the 'kill switch' you encountered, so if it does happen again you'll be annoyed by pop-ups instead of a nearly crippled system.
I bought a GM5632E in November 2007. It worked fine up until mid-December, when it started suffering from the internet-documented restart problem. I changed a couple of BIOS settings, which seemed to alleviate the problem. . .
. . .until early January. I read about the problem on other forums, and downloaded and installed a BIOS update from Gateway. This did nothing, and so I probed further, looking for any solution I could.
In retrospect, I know I shouldn't have done this (I've learned my lesson). . .but, I downloaded and installed a BIOS update directly from the Intel website for my motherboard. This resulted in resolving the restart symptom. . .but, caused the computer to report on startup that "The AA number is not installed on the system. Press Enter to continue." Seeing this as a small side effect, I would always proceed. . .assuming there was no problem. . .
. . .until I started getting Windows Activation screens coming up on my computer, once I logged into Windows. At first, I couldn't really pinpoint what I was doing that would cause them to appear, but I would ignore them, and continue. This went on for three days, until I was confronted with an activation screen, which limited me to a reduced functionality mode, or typing a different Microsoft Windows product key, or contacting Gateway for support. Various diagnosing resulted in the following:
1. Putting in my product key would result in the system attempting to reach the licensing server, before reporting error 0xC004E003, with a message "The Software Licensing Service reported that license evaluation failed."
2. Running the Microsoft Genuine Advantage Diagnostic Tool would report that I had an invalid license.
3. I checked my product key with Microsoft tech support, and they told me that I had a valid license key.
I'll spare the details of tech support (Microsoft telling me it was Gateway's problem, Gateway telling me it was Microsoft's problem, etc.), but Gateway told me to return the system to a prior restore point. . .and if that didn't work, completely restore the system. I ended up needing to completely restore the system, and the problem went away. . .
. . .until this month. I went through the same activation screen symptoms, and eventually found a BIOS update on Gateway's website, published 2/4/2008, which solved all of my problems.
(For anyone suffering from the restart symptoms for this system, the update is at: http://support.gateway.com/support/drivers/getFile.asp?id=21708&uid=186679562)
I flashed the BIOS, and waited for the rest of the startup routine. The login screen came up at what looked like a 640x480 resolution, and then when I logged in, this resolution remained, with a message in the bottom right hand corner saying "Windows Vista (TM) / Build 6000 / This copy of Windows is not genuine", which was a message I had the entire time that I was having the issues with the Windows Activation screen. Also, the device driver installation routine was running like crazy, as it was reinstalling the drivers for all of my hardware, which I was surprised by. When it stopped running, I restarted my computer one more time, and everything was back to normal. I have suffered no problems since.
So, really. . .I'm posting this for two reasons. One, to help anyone who has the same system that I do. Flash your BIOS with the new update from Gateway, and I hope it works for you. But, number two. . .if anyone has any insight as to why flashing my Gateway BIOS with an Intel update would cause my Microsoft Windows Vista software to act corrupt, I would really like to know. And also, why did all the drivers for all of my hardware devices have to reinstall, before my copy of Windows was reported as being genuine?