Multipart archives are a common way to hide malicious code. Since antivirus software sometimes struggles to scan a fragmented file until it is fully reconstructed, a "Pack" could be a Trojan horse.
Here is an analysis of what that file represents and the risks associated with it. The Anatomy of a Multipart Archive
Part 04 is useless without the rest of the set. If the other parts are deleted or missing from the host, this file is just digital dead weight. Pack.part04.rar
"Pack.part04.rar" is a ghost of a larger file. By itself, it is a locked box with no key. If you found this on your hard drive, it's likely a leftover from a failed or forgotten download. Unless you have the accompanying parts and a trusted source for what was inside, it is generally considered safe to delete.
Finding information on a specific file like is a bit like finding a single brick in a skyscraper. Without the context of the original download or the community it came from, it’s an anonymous piece of a larger puzzle. Multipart archives are a common way to hide malicious code
Downloading isolated .rar parts from the internet carries significant risks:
If even one byte is missing or corrupted in part 04, the entire parent file usually fails to extract, rendering the whole set broken. Conclusion The Anatomy of a Multipart Archive Part 04
Do you have the of this archive, or are you trying to recover the contents of a corrupted set?