By following the tutorial I had two issues that I want to expose here, in order that I can help other players.
First of all, I was not able to obtain the GUID because punkbuster was not enable. To activate the punkbuster must access the command line and type: / pb_cl_enable - With the punkbuster enable you should have no problems to obtain your GUID.
Then, I don't know why, I never get the .txt file with the GUID, anyway, if you look, when you write / pb_myguid you already get the GUID in the command line. It's not as practical as having a .txt file with the number, but you can get it in it .
Hope my issues can help you!