Instructions
Load "StarCraft 2" and select the options menu from the main login screen.
Click on the graphics tab to select graphics options.
Set the texture quality, graphics quality, shaders, lighting, shadows, terrain and effects to the lowest level.
Turn reflections off, set the unit portraits to 2D, and set the post-processing, physics and models to low.
Click "OK" to save changes. You will need to restart the "StarCraft 2" client in order for the changes to take effect.