A lot of people are still using torrents and other methods to download any Blizzard game. This way is much easier and 100% safe.

1. First of all, you require a CD key for the specific game [can be muted/voided].
2. When you get a CD key, go here and register an account.
3. After you are done registering your account, go here and then click Add a New Game.
4. Then you enter in the CD key for the game, and it will bring you back to the main page.
5. Simply go to the game that it showed you registered and then click the manage game option. There should be a windows/mac download link provided here.
6. The link will supply you with the Blizzard Downloader.
7. The Blizzard Downloader will download the setup files for the selected game.
8. Once you download the setup files, just simply install, and they will work without a CD.