Due to the specifications of Windows® XP Service Pack 1 (SP1) to improve stability and provide better performance, the following types of files cannot be shown in the thumbnail view after the installation of SP1.
.EML files (Internet E-mail massages)
.NWS files (Internet News messages)
For more information, please refer to the following solution in Microsoft's technical support website.
Article ID: Q327833
Last Modified: September 09, 2002
Title: Cannot View Web Content Files in Thumbnails View