title: Can not install Android ADT 21.1 on eclipse Juno (Windows 7) after upadate to SDK 21.1
body: <p>I have download ADT 21.1, and tried install it on eclipse
  <img src="https://i.stack.imgur.com/w8EUH.jpg" alt="enter image description here"></p>
  
  <p>I got those:</p>
  
  <p>The operation cannot be completed.  See the details.</p>
  
  <p>Details:</p>
  
  <p>Cannot complete the request.  See the error log for details.</p>
  
  <p>Tracer for OpenGL ES will be ignored because it is already installed, and updates are not permitted.</p>
  
  <p>Android DDMS will be ignored because it is already installed, and updates are not permitted.</p>
  
  <p>Android Development Tools will be ignored because it is already installed, and updates are not permitted.</p>
  
  <p>Android Traceview will be ignored because it is already installed, and updates are not permitted.</p>
  
  <p>Android Hierarchy Viewer will be ignored because it is already installed, and updates are not permitted.</p>
  
  <p><img src="https://i.stack.imgur.com/gwFSf.jpg" alt="enter image description here"></p>
  
  <p>When I reopen SDK Manager, I still got this:
  <img src="https://i.stack.imgur.com/Oa3lN.jpg" alt="enter image description here"></p>
  
  <p>In Windows->Preference->Android, I got this:
  <img src="https://i.stack.imgur.com/egAM6.jpg" alt="enter image description here"></p>
  
  <p>Thus, I wanna reintall ADT, but I found I can't uninstall any Plug In, Uninstall.. button is gray!
  <img src="https://i.stack.imgur.com/cxSrw.jpg" alt="enter image description here"></p>