This usually means part2 was not fully downloaded or the file size does not match the other parts in the set.
To extract the game, you must have DiRT4.part1.rar present. Opening "part1" with a tool like WinRAR or 7-Zip will automatically "bridge" to "part2" and subsequent files. Common Issues
This error occurs if you try to extract the files without having all the numbered parts in the same directory.