a corporate copy really isn't the correct term..
Companies purchase Microsoft software with a license that is known as "Volume Licensing". This allows a certain product to be installed on multiple systems, usually with the same key, as long as the license agreements are still met.. etc.. etc..
But, I know here at work, even with "corporate" installs, you still have to enter the license key, at least with Windows 2000 Server & Advanced Server..
That is why I am supspected that your copy has the key integrated in, with an unattended Answer file, or whatever other way the hackers wanna do it these days..