From Intense Ragnarok Online Wiki
To fix this problem follow these steps.
- 1. Open control panel, and find "Regional and languages".
- 2. Go to "Administrative" Tab.
- 3. Press "Change system locale"
- 4. Change it to the "English, United States"
- 5. It will ask you to restart your computer.
- 6. After your restart you should be able to install.
After installation you can change your language setting back to the original setting. Basically, the problem is your computer Unicode setting. If your setting is set to international language such as "China, Korea, etc". Then this error would appear. Just by changing to to English would solve the problem.