Installing wow Problems.

[Noobkiller1x]

I recently got a cactalycim beta invite and wanted to install it so I did. It said I needed the wow wotlk patches so I decided to activate my trial. I then downloaded the game client and it doesn't work at all it says that I need to close all aplications (Which I have tried doing.) And failed to create directory when theres already a directory made it also gives me a text file. Any solutions?
Hopefully someone can help.

[Cane]

I'm sure you need the full game installed... aka Vanilla & TBC.