Windows 7 to Windows Vista?

I've recently made a mistake of reinstalling my operating system from Windows 7 to Windows Vista because my computer was infected with a virus that I didn't know how to repair. My computer originally came with Windows 7 as it's operating system but silly me, I reinstalled it with Vista and have deleted all my old windows files. Now my computer won't recognize the ethernet controller + other hardware on the computer and won't let me connect to the internet. Will I have to buy a new windows 7 to fix this problem? Please help me out. :(