" Just copy the font to the Font Directory located at C:\Windows\Fonts which will install it for the system to use. The other method is to click on the font file at its current location. It will then give you a screen that shows the font preview and there you will see the button to install the font right at the top of the screen toward the left side."
or this:
http://www.sevenforums.com/tutorials/1155-fonts-install.html
