Error when i add to Visual Studio 2008 Toolbox

[obiwan74]

hi,
i use Visual Studio 2008 SP1 and ext.net 1.3. (Windows 7 x64)
I changed my pc but when i install the library in the toolbox displays an error:

Could not load file or assembly 'Newtonsoft.Json, Version=4.0.8.0,
Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed' or one of its dependencies.

I downloaded the latest version of Newtonsoft.Json from
http://json.codeplex.com/releases/view/89222
but always appears the error!

thanks

[obiwan74]

can anyone help me?
thanks