Well, i have done the next, i have run Tweak! and choose the options i posted before.
I have created a new user: dodgy.user@hotmail.com (password: chungocubata), and then i have signed in Msn Messenger with this new user, but i checked the "Start automatically" option in the Sign In window, setting this new account as default account, so, the Setup Wizard has not started in this new account.
It's not the optimal solution, but it's a solution, the user only has to sign off Msn Messenger and check "Forget my account" before leaving the cibercafe.
PD: Now, the owner has only to write a long instructions lis in each PC to the Msn Messenger users
