hi there honestly dont listen all this bull s**t, in my experience i use them , like example what i do if i have a change to see genuine key like you see on all dell computers, i copy them , download windows 7 pro clean copy *untouched* install windows 7 pro and no mater what dont add the key straight away after install what you need to do go to my computer system properties and on the bottom it says windows activation, so you what need to do just click on change product key and job is done, that is what i am doing, but dont mix up if you windows sticker where it says on windows home pre then you need to install windows home pre, not pro good luck