Although RefWorks has a tool to find Duplicate references, it might be safer to keep them than to delete one that you have already used in Write-N-Cite, or one that your are depending on having in several folders.
RefWorks Add-on for Microsoft Word and Google Docs
RefWorks has free add-ons available for Word and Google Docs. They allow you to add citations and automatically create bibliographies within Word or Google Docs. More info at the links below.