Visual Studio have a nice integration of Extensions. Sometime when you want a feature you can easily got extensions (plugins) from Visual Studio gallery. Sometime some user have trouble the performance in VS when they got install too many plugins.
For removing all extensions in Visual studio manually You need to open Window explorer CTRL + E and type %LocalAppData%\Microsoft\VisualStudio\10.0\Extensions. and press enter. This show you a folder which contain all plugins if you delete them then this will remove all plugins from your visual studio 10 installation.
Note:- This thing work fine on my computer. You need to remember then your Visual studio is sleep or not running when are delete the folder.