I just want to share a quick tip about something really smooth that many IT staff seems to be unaware of. Windows Vista and Windows Server 2008 introduced the fact that you can install it without entering a product key. This was later introduced in Windows XP (with service pack 3 slipstreamed) and also later Windows Server 2003 R2 media. Nothing about this changes for Windows 7 or Windows Server 2008 R2. So to sum it up you can install all current as well as coming operating systems without entering a product key and you will then have up to 30 days to enter it.