Word has no functionality for doing that kind of thing.

The nearest you could get to that with Word is to insert transparent textboxes over the image, each containing a bookmark to which you create a hyperlink in the same textbox. If you make the hyperlink text transparent (e.g. a 1pt period and a bunch of spaces), with your hover text as the screen tip, you'll be able to get that to pop up when you click on the textbox then hover over that part of the image. However, that's quite clunky and you'll also have no control over the hover text placement; it'll also display 'Click to follow link', which is hardly what I imagine you'd want...

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]