This article will analyze the recent U.S. and E.U. judicial approaches to tying charges which stem from software bundling. Part II reviews U.S. tying jurisprudence both generally and as applied to software bundling. Part III outlines the D.C. Circuit’s approach to Microsoft’s Windows/Internet Explorer bundle. Part IV briefly covers tying jurisprudence in the European Union. Part V describes the European Commission’s (“E.C.”) analysis of Microsoft’s Window/Windows Media Player bundle. By comparing the two approaches, Part VI shows that neither approach is ideal: although the U.S. approach offers too little guidance to software manufacturers seeking to avoid liability and unduly discounts potential losses in innovation from excluded competitors, the E.U. approach stifles dominant software firm innovation and efficiency because the approach is too rigid and formalistic.