Since their is alot of unclear posts of "how" to do this and things going wrong, i have uploaded the Client installer (+downloader) and the sandbox in one RaR for you.

this is the EU client only

http://rapidshare.com/files/38564014...lient.rar.html

1. Make sure you have the latest wow patch up to date

2. Install the client

3. Run the sandbox

4. Change your realmlist to 127.0.0.1 ( if your realmlist.wtf resets when you close it, go to data > engb > realmlist.wtf

now run the game and log in with any name and password.

The alpha is unstable all round so be careful when exploring because crashes WILL happen.