Why would you buy a new copy of Windows 7 OS when you paid for one with your laptop? You own
a MS Windows 7 license, not a crapified version of it your OEM says you must have so they can wring extra profit out of the sponsors' bloatware.
Many if not most tech enthusiasts clean reinstall using a Windows 7 installation DVD they find, borrrow or download from the web to activate with the Product key on COA sticker.
Here's how to get a perfect CLEAN reinstall of Windows 7 factory OEM based on hundreds done here: Reinstalling Windows 7