Come on, help yourself a bit here. Just because you've asked for help on a forum doesn't mean you can then switch-off your brain and do no troubleshooting at all yourself.
Did you read the docs for <cfspreadsheet>? What version of CF was it added in? What version of CF are you running? Even the error message gives a very strong clue as to what the story is here:
This tag is not supported by this version of ColdFusion
So you're using CF8 or lower (if you're using an obsolete version of CF, you really ought to mention this in your initial post), so <cfspreadsheet> is not available to you.
So you'll need to use POI. Google it. Hint: Ben Nadel has written a CF wrapper for it.
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Adam