Instructions
Changing the Resolution of "Warcraft III: The Frozen Throne"
Open up your Windows Registry by opening your Start menu, typing "regedit" into the search bar and hitting "Enter." If you do not have Windows 7, you will have to select Run before typing "regedit."
Locate the registry entry titled "HKEY_CURRENT_USER > Software > Blizzard Entertainment > Warcraft III > Video"
Find "resheight" on the list and change the number to the desired height in pixels.
Find "reswidth" on the list and change the number to the desired width in pixels.
Close the registry and start your game.