Because this is labeled , you cannot extract the game using this file alone.
You should use a utility like WinRAR or 7-Zip . Right-click on only part1 and select "Extract Here." The software will automatically pull data from the other parts to recreate the full game folder. SexNote-0.19.5a-pc.part1.rar
Always run a virus scan on extracted .exe files, as multi-part archives from unofficial mirrors can sometimes be used to bundle unwanted software. Because this is labeled , you cannot extract