Where can I find that variable and how can I change it?
In Windows 7, for example:
1. From the desktop, right-click My Computer and click Properties.
2. On the left side menu, click Advanced system settings.
3. In the System Properties window, click on the Advanced tab.
4. In the Advanced section, click the Environment Variables button.
5. Under User variables for your username, click New... and set up a new environment variable "SDL_RENDER_DRVER" with the value "opengl" as highlighted in the attached image.
This bug will be more or less fixed in the next release, so be sure to wind this change back when you get IVAN 0.50.7