Somehow I found that there are some useful functions in paint that can help your graphics design at
http://www.albinoblacksheep.com/tutorial/mspaint
Summary of skills which are the most useful:
Enlarge/Shrink Sprites
Select/highlight a region, then press Ctrl+Plus to enlarge it or Ctrl-Minus to shrink it.

Colour Replacement
Select the eraser tool.
In the primary color box, select the color that you want to erase.
In the secondary color box, select the color you want to replace with.
Then hold right click and sweep with the eraser tool over the ugly color.
If your drawing is large, scale the eraser brush as needed.


Grid Tool
Press Ctrl-G to toggle the grid, zoom in the image for a smaller grid.

More on the website mentioned. I hope this can help everyone to draw sprites easier.
I tested with Paint in Windows 7 and all worked, it should also work in other versions (please check for 95, 98, Me, 2000, XP, Vista).