Searching for an "Index of Windows 7 Themes" usually refers to finding open directories (server file listings) that host legacy .themepack
Benefits of Indexing Windows 7 Themes
Community Sites: Websites like DeviantArt host thousands of custom Windows 7 "Visual Styles" (which require system patching to use). Intitle Index Of Windows 7 Themes
The title tag of a webpage usually describes the content of the page. When a web server generates a default directory listing (a list of files in a folder without an index.html or index.php file present), the title tag is often automatically generated as "Index of [directory path]." Searching for an "Index of Windows 7 Themes"
