How do you open XML Schema Explorer

I solved it as follows:

I created a new file of type 'XML Schema'. That opened up the XML Schema Explorer. Then I switched to my file and the XML Schema Explorer window stayed open.

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In VS2010:

1. Right click on your existing .xsd file and select "open with".
2. Select "XML Schema Designer"
3. Then in the template that comes up, click the link that says "XML Schema Explorer".