Export>Word (HTML) is useful within limits.

1. It works if your outline has five or less levels of nesting. Beyond header level 6 all rows are flattened to Normal paragraphs in Word.
2. It does not properly handle the export of columns.

Finding a Windows app that reads/writes OPML of arbitrary nesting depth should not be impossible.

The search for a Windows app that correctly interprets OO columns from OPML will be harder, as they are encoded as non-standard OPML attributes.

It might be worth looking at the OO Exports Plug-in on the OO Extras Page

One of the supported export formats is Excel XML.