Remove unused using in Visual Studio 2008
Even though, include many "using" namespace will not affect the performance when runtime, but it will affect your Intellisense performance. When you type something, Visual Studio's intellisense will search the associated work you typed with existing keyword, type, identifier, etc. The more "using" namespace you put, the more list of match word will be load.
Luckily, in Visual Studio 2008, we could remove unused using. It will automatically, remove all using that actually we don't use in our code.
To use it, you could simple choose Edit - Intellisense - Organize Using - Remove Unused Using
Beside it, you also could sort the using in ascending order. It will help you easier to read.