: If you are using a non-Steam retail version, Bohemia released a specific Reinforcements DLC Setup Utility to help manage these expansions. Arma 2 Official Website Troubleshooting Admin Rights
Bohemia Interactive has moved all future updates to the Steam platform. You can now activate your legacy retail keys directly through the Steam client. Arma 2 Official Website Run as Administrator: For the smoothest activation, ensure the Steam Client is running with administrator privileges. Product Activation: In the top menu, click arma+2+reinforcements+cd+key+updated