Thank you for your reply solving my problem.
My problem was to open the ATi Catalyst Control Center. Every time I start up my computer, a message looks like the message of the top of this page, appears in my screen, and the ATi CCC couldn't open. Now, I've re-installed the Microsoft .NET Framework
and looks like my problem with this have been solved, but for this moment, my Windows Live Messenger is crashing when I click to Sign Up. I've tried to reinstall it but looks like it haven't a good condition now.
What I can do to fix it?
(Sorry for my bad english, it's because I'm brazilian... and here we haven't a way to practice it. Thanks for the support!)