I have Eclipse (Indigo Service Release 1, Build id: 20110916-0149) running on Win XP.
I\'ve added https://dl-ssl.google.com/android/eclipse/ and installed 4 plugins
Q: Did you install the Android SDK?
You need to do this in addition to installing a) Java, b) Eclipse and c) the Android plugins for Eclipse
Here's one (of many!) "Quick Start Guides" for setting up Android on your development PC:
http://www.talkandroid.com/guides/developer/android-sdk-install-guide/
PS: Please don't "unpack" anything, except unzipping Eclipse itself.
You might actually wish to delete your install and re-install from scratch (just to make sure there isn't anything "weird" in your environment).