If you come across the error in the picture below, continue reading.
Step 1: Open Lunar Client's properties
- Right click on Lunar Client's setup application.
- Click on the "Properties" button.
Step 2: Change compatibility mode
- Press on the "Compatibility" tab.
- Tick the box that says "Run this program in compatibility mode for". The default should be Windows 8.
- Press the "Apply" button at the bottom.