See if this helps. The default text size has been an issue for me since Windows 7. I'm not sure why this is, maybe someone else can help there. Something about windows trying to "zoom-in" on small applications and making them blurry.
- Right-click on the desktop and click "Screen Resolution"
- Click "Make text and other items larger or smaller"
- Choose the smallest setting.
- Apply changes / press OK and close the windows.
- Log out and back in to see changes.
If that doesn't help, return to the "Make text and other items larger or smaller" page and play around with "Adjust ClearType Text" and "Set custom text size (DPI)" on the left. As above, the less you zoom in, the clearer (but smaller) things will be.