「作業系統軟體」與傳統「實體產品」具有本質上差異，軟體產品缺乏實體產品具有的實體外觀界線；因此，當數件不同功能的「應用軟體」，搭載於同一「作業系統軟體」上時 (例如，將文書處理軟體Word、PowerPoint等，安裝於作業系統軟體Windows上時)，則係該本可區分的「數件」不同功能軟體，此時於外觀上將有別於傳統「實體」產品，吾人難僅由其外觀，利用直覺來區分產品的個數。質言之，當一件「應用軟體」安裝於一件「作業系統軟體」上時，此時究竟是應認為存在有「兩件」可區分之軟體產品？還是應該認為，只有「一件」包含該應用軟體功能的作業系統軟體產品存在？產生爭議。 由於反托拉斯法上的「搭售」行為，至少需要有「兩件」以上的產品，同時綑綁於一起販售，始有可能構成。故而，「作業系統軟體」其可搭載他種「應用軟體」的「平台特性」，以及其異於傳統「實體產品」的「去實體」特性，使得作業系統一旦與其他應用軟體結合，則在適用反托拉斯法相關搭售規範時，首先於『是否存在兩件以上可分的「個別產品」』？此一違法搭售的最基本構成要件認定上，就發生疑義。因此，反托拉斯法上違法搭售行為的構成要件中，認定是否存在「搭售產品」與「被搭售產品」的「個別產品要件」，於「作業系統軟體」此類非實體的產品發生搭售爭議時，其判斷標準究竟為何？值得吾人加以討論與研究。 知名軟體廠商美國微軟公司 (Microsoft Corporation)，於1998年5月，遭到美國司法部與美國二十個州的檢察長指控其涉嫌違反反托拉斯法，而衍生出全球囑目的美國微軟案。該案最具爭議的部分，乃是美國微軟公司其所生產的「視窗作業系統軟體」與「網路瀏覽器軟體」結合於一起販售，涉嫌違反美國反托拉斯法的搭售相關規定。 本論文將嘗試說明，「作業系統軟體」其究竟如何引發反托拉斯法上之搭售爭議？美國微軟案其所引發的搭售爭議關鍵爭點究竟為何？配合釐清美國聯邦最高法院所作的搭售相關重要判決與其所揭櫫之重要原理原則，對照分析美國微軟案聯邦地方法院與上訴法院之判決理由，思考就違法搭售爭議案件中，關於是否存在兩件以上可分的「個別產品」相關認定理論，例如「功能關係理論」、「顧客需求理論」之可行性與適用性。

The software of an operating system (hereafter referred to as OS) is substantially different from concrete products. In that software is not tangible, it is difficult, at best, to determine the number of “products” on the basis of appearance when there are several application software products installed in one OS. That is, for example, we are hard pressed when it comes to counting the exact number of “products” when both “Microsoft Word” and “Microsoft PowerPoint” are installed in one Windows OS. Under the American Antitrust Law, an illegal tying arrangement is sustained when at least two products are bound together for sale as one unit. Thus, when an application software product is installed in an OS, the crucial issue is how to determine whether the OS should be regarded as two separate software products, or as only one OS product that contains the functions of the application software. In other words, carrying other application software functions as a platform, particular1y in view of their intangibility, makes it difficu1t to clear1y define whether it is one or two products once the OS has been integrated with other application software functions. Understandably, this has fundamentally challenged the way the Antitrust Law defines a “tying arrangement”. On May 18, 1998, the United Sates Department of Justice and dozens of state attorney-generals filed an antitrust suit against Microsoft Corporation. The most contentious issue was the very question as to how to determine whether they should be regarded as two separate software products or only as one when Microsoft proceeded with its contractual and technological bundling of the IE web browser with its Windows operating system. This paper explores the circumstances under which the manufacturer of an OS may be in violation of a tying arrangement under the Antitrust Law. Taking into consideration the U.S. Supreme Court’s precedent and comparing the viewpoints of the district court and the appeal court toward the Microsoft case, we seek appropriate criteria so as to be in a better position to determine whether the integration of an OS with application software should be regarded as two separate software products, or as only one OS product which contains the function of the application software.