All numbered parts must be in the same folder. You must open the .001 file specifically to begin the extraction process.
This file cannot be opened or extracted without part .001 (and potentially .003 , .004 , etc.). Requirement for Extraction SS-Kat-017_s.7z.002
: Use the latest version of 7-Zip or WinRAR. Right-click the .001 file and select "Extract here." All numbered parts must be in the same folder