1) Open Windows Explorer.
2) Navigate to the C:\Windows\Fonts folder.
3) Choose File -> Install New Font
from the menu.
4) A dialog will popup. Navigate to the folder that contains your new fonts (TTF files) to install.
5) Click the Select All
button and then click the OK
6) All the highlighted fonts will now install.install many fonts with one click
Alternately, you can just drag-n-drop multiple TTF files into the c:\Windows\Fonts folder and they will install. If you're using Win2k, the path will be c:\Winnt\Fonts.