我写信去官方问了
也真的回信给我
也确定这是属实的
我刚刚确定是可以下载
只要你有正版的CD-Key

1) Visit www.blizzard.com/store
2) Click on the "Register" link on the top-right corner of the page
3) Follow the steps in order to create a Blizzard Account
4) Once you have created a Blizzard Account, log in and click on the "Account" (right next to My Orders and Logout)
5) Under the "My Account Controls" click on the "Games" button (it has a picture of an Orc on it)
6) Click on the "Add a New Game" button to register your games' CD-Keys. After you have done this, your games will be available for download from this page. Remember to use the new CD-Keys listed on this page in order to install the games.

主要就是藉由blizzard store注册帐号后直接输入序号下载
我假设大家英文都很好
就不翻译了(其实是懒)