To install a font downloaded under Windows 7 there are several methods. Indeed you can either install the font manually by placing the .ttf file in Windows folder named "fonts" and launch the automatic installation.
Download the desired font from dafont or others legal website.
Put the .TTF file in the Windows directory(Fonts):
Double click on the .TTF file.
Click the Install button.
Then, go in
"Appearance and Theme"
Add the .TTF file in the Font folder.
Extract the.TTF file to archive using WinRAR or 7zip.