Enable Pixel Preview
The Pixel Preview feature lets you preview your artwork in Microsoft Expression Design to see how it will look after you export it as a bitmapped image. When you enable the Pixel Preview display mode, vector strokes and fills are rasterized (turned into a bitmapped image) for on-screen viewing. Therefore, when you zoom in on a path, the edges will appear bitmapped (pixilated).
To enable Pixel Preview
On the View menu, click Pixel Preview.
To disable Pixel Preview
On the View menu, clear Pixel Preview.