Right-click the left_4_dead_v1027.zip file > Scan with antivirus. Look for .exe files inside that have random names (e.g., setup_123.exe )—that is usually a virus. A clean repack usually has a single setup.exe or just the raw game folder.
: Open your .zip archive (e.g., left4dead_v1027.zip ) and extract all contents into a new folder on your computer. file left 4 dead v1027zip install