A Youtube user found that by changing the clock on your machine to when the offer was still available it will let you get the free upgrade.
Once the clock has been changed to July 28th, the prompt will provide the option to start the upgrade. After clicking that, it will begin downloading Windows 10 and the installation will commence.
There is also another method by entering a windows 7 key to activate a windows 10 instillation.
If you still want the free windows 10 upgrade give us a call any time!