Finding specific "part4" files can be tricky if the original source link is broken or hidden. 1. Identifying the Source
Instead of searching for "part4" specifically, search for the full string "HV530 PC821 3840x2160" on the site where you found the first three parts.
Ensure the file extension is truly .rar .
The naming convention HV530 PC821 suggests this is part of a specific release series.