Microsoft.
...yeah this is exactly why it's doing this.
I'm pretty sure Microsoft's drivers include barely any support for OpenGL but include massive amounts of support for DirectX. It's bias, but the first thing you're supposed to do when you install new hardware (or reinstall the OS) is
obtain proper drivers from the manufacturer. In this case, you can obtain the proper ones for Windows Vista & 7
32-bit, or
64-bit.
Follow the installation instructions, restart your computer, start up Blockland, enjoy shaders.