Seems like a bit of a joke to me. With my Gateway pre-installed key I get:
The product key you entered appears to be for software that was pre-installed on a device. Please contact the device manufacturer for software recovery options.
Ahhh...OK. So I dug out my retail disk and punched in the code. I get a quick flash of the screen with no results, or:
Unsupported Language Error
The language you have selected is not available for the product you are eligible for. Please select a different language.
What was the language you ask? English! I tried a few other languages with the same result.