Microsoft Knowledge Base Article 926141 contains the following INTRODUCTION:
This article describes the installation packages for the Multilingual User Interface Pack (MUI) Language Packs for Windows PowerShell 1.0 on Microsoft Windows Server 2003 Service Pack 1 (SP1) and on Microsoft Windows XP Service Pack 2 (SP2). These packages automatically install the Release to Web (RTW) versions of Windows PowerShell 1.0. Also, these packages are later versions of the release candidate versions of the product.
The Windows PowerShell 1.0 MUI Language Pack displays the Windows PowerShell 1.0 user interface in Chinese Simplified, Chinese Traditional, French, German, Italian, Japanese, Korean, Portuguese, Russian, and Spanish.
The MUI Language Packs run only on MUI versions of Windows, in which the Windows interface can be displayed in multiple languages. If you are running an MUI version of Windows, install the English version of Windows PowerShell 1.0, and then install the MUI Language Pack for Windows PowerShell 1.0.