Hl_001_2.7z

: Ensure all parts have the exact same base filename, differing only by the sequence number at the end.

: Right-click only on the file ending in .001 . HL_001_2.7z

Do you have of the file (like .002, .003), or are you missing the rest of the set? : Ensure all parts have the exact same

: If you see a "Cannot open file as archive" error, the header may be damaged. You can try opening it in a hex editor to verify the start and end headers. HL_001_2.7z