You cannot degrade your laptop's operating system. I know how you feel. Once I bought my laptop with Windows 8 I was so peeved off and hated it. But, it has been about 6 months and I am finally use to Windows 8 and I actually love it. My mom and step dad just bought a laptop with Windows 8 and they hate it. I think they will like it in time.
You can't without buying a copy of Windows 7 and changing the default operating system. I recommend either taking it to a shop that will do it or just staying with Windows 8. It's not that bad if you aren't using the computer for gaming.
There is not other option you have to buy it because downloading may cause virus or trojans and it can work very slowly and if you buy it. It would way better from downloading cause it will be orignal. You have to ask the person you have brought from he will surely help how to format and download Windows 7. May it will help
Microsoft is strict when it comes to downgrading operating systems. They would only provide a free downgrade if your computer comes with windows 8 professional to win7 or winVista. What you can do is purchase windows 7 retail and full version or you can return that to your reseller and exchange for a windows 7 os.