Quick Answer: Make sure that YourRO is running from a fresh installation with the latest files. Check your graphics settings in RagnarokSetup.exe. If on Windows 8, check your DirectX settings. Finally, check to see if your Microsoft Visual C++ is up to date using the download link below.
Be sure that you’ve installed YourRO into the proper directory and that you’re running off of a fresh installation. This ought to resolve most issues. You may also be experiencing a problem with your graphics card and/or gameplay resolution. In your RO folder, click on the Setup.exe
Check if in the Rendering Engine and Sound boxes there are options to be chosen, if there are, choose one (or change) and go with next step.
If one of the box is blank, with no options to be chosen, means likely that you have no drivers, they need an update, or that you need to enable hardware acceleration (in the DirectX options box) to make it work.
Check RagnarokSetup.exe again.
In any case, adjust your screen settings to fit best with your PC’s specifications. Try disabling full screen mode and lower your resolution to see if this works.
If you are running Windows 8: This may be due to a setting in your DirectX configuration. Go into your DirectX Control Panel and select DirectDraw. Under performance check "Use Hardware Acceleration" and click OK.
You may also need to check to see that your version of Microsoft Visual C++ is up to date - installing at least each of the successive Microsoft Visual C++ Redistributable Package (x86) starting from the year that you have currently installed through the most currently available package. In most cases, installing this and rebooting your computer should solve this error.
Before installing, confirm that you don't have any of the soft mentioned. Check them out on "Add/Remove Programs" from your Control Panel. They should appear there if you have installed them. Most people will already have 2005, so it's best to try the 2008 version first. Keep in mind that having 2010 does not mean you have all the necessary files that are in the 2008 version. So even if you have the 2010 version, install these anyway if you don't have them.
Download and install the following VC++ Redistributables:
Visual C++ 2008 SP1 Redistributable Package (x86)