What Sonia said and ...
Other than the tools that let you draw during slide show mode,
PowerPoint, using Drawing, not Painting. In Drawing, you are drawing
objects. You can select these objects and change the attributes of them
(such as size, color, fill, etc.), but you can't erase dots. That's
something that is done in painting applications that don't paint object,
but paint a bunch of dots that look like objects. Thus, in Painting, you
might think you are drawing a rectangle, but you are drawing a bunch of
independent dots that look like a rectangle. It is harder to change the
attributes of what is painted, but since all the dots are really
independent, you can erase individual ones or groups of dots with an
eraser tool.
--David
--
David M. Marcovitz
Microsoft PowerPoint MVP
Director of Graduate Programs in Educational Technology
Loyola College in Maryland
Author of _Powerful PowerPoint for Educators_
http://www.loyola.edu/education/PowerfulPowerPoint/