How to: Erase a very small area in Paint.
Solution:
Use the smallest eraser tool.
NOTE: This solution assumes that Paint is opened.
1) Click the eraser tool in the tool box.
Eraser tool
2) Click the smallest size for the eraser in the tool box.
3) Click and drag the mouse pointer over the item to be erased.
NOTE: To make the most accurate erasures, zoom the picture to a larger size.