I downloaded and installed SilverLight 4.0 tools for WP7 but I am unable to attach some controls. When "choose items" option on toolbox, I search for a System.Windows.Controls library and, once attached, I can see tabBar object properly selected and ready to be attached. However, after accept, control does not appear on toolbox. Am I doing something wrong? Thank you.
There is no TabControl in the Windows Phone toolkit.
You've probably selected a dll that also contains a System.Windows.Controls namespace, that is not compatible with Windows Phone 7 development.
EDIT
The article referenced dotnet.dzone.com/articles/using-tabcontrol-windows-phone uses the TabControl from the standard Silverlight controls. The way I read the article, the intention is to add a reference to the library mentioned to a Silverlight for WP project (i.e. "Add Reference" from the "References" node of a project), and working from there.
It won't show up on the toolbox, that's for sure.