ADTr20 doesnt get installed in my eclipse
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I have updated my android sdk to sdkr20, before i used r16 and my eclipse version is 

Version: Indigo Service Release 1
Build id: 20110916-0149

but when I try to install ADTr20 it doesnt get installed and says

Cannot complete the install because one or more required items could not be found.
  Software being installed: Android Native Development Tools 20.0.0.v201206242043-391819 (com.android.ide.eclipse.ndk.feature.group 20.0.0.v201206242043-391819)

what should I do now?