The correct answer is to utilize a reputable third-party uninstaller program designed specifically for removing stubborn software. These types of programs are engineered to clean up residual files and registry entries, which the standard 'Add/Remove Programs' feature may miss, particularly when dealing with uncooperative software. Reinstalling the operating system is an extreme measure that would indeed remove the unwanted software but is not practical and involves unnecessary risks and data loss unless all other options are exhausted. Force deleting files could corrupt the system if essential files are accidentally removed. Installing additional antivirus programs is not related to the removal of non-malicious unwanted software, and running multiple antivirus programs can cause conflicts and system instability.