You could always download the Windows 7 Enterprise 90-day trial which is the final version of Windows 7. By the time the trial runs out, Windows 7 will be available to purchase.
Is it possible to turn the trial into the full product as and when our Volume Licensing agreement is amended? Just curious as it says that the product key is embedded.
Or would it involve a rebuild?
Use this until you can get a real version of 7. Buy it now, whilst it's still cheap