I solved it! This was ****ing me off for the longest time! I actually redownloaded the beta client 3 times, all to no avail. Everytime I would try to extract the files, it came up as corrupt or multi-zip error or something like that. So I assumed the file was corrupt. After trying 3 times and from different sites, I kept getting the same error, so I changed my assumption that if the file isn't corrupt, maybe the program I'm using isn't working right... and I was right! I was using WinRAR to unpack the files, which has never given me a problem. But I tried the 7-zip built into Windows 7 and it worked! It unpacked it and the .EXE appeared. So use 7-zip to un-compress the file and it should work. It did for me!