To the average user, the phrase looks like a garbled piece of code. However, to anyone versed in advanced search operators (Google dorking), it is a precise key that unlocks unlisted directories on the web.
Unlike official repositories, files in an open directory are unvetted. A .themepack file is essentially a CAB file; while generally safe, accompanying .exe files in the same directory (often "theme patchers") can be malicious.
(used by later versions but often compatible) within publicly accessible server indexes. Recommended Search Queries Copy and paste these into Google to find open directories: Standard Theme Packs: intitle:"index of" "windows 7" "themes" .themepack Exclusive/Premium Keywords: