Paint>View>Zoom>Large View
Paint>View>Zoom>Show Grid
The image must be enlarged for the option to become available.
As a shortcut, you can press Ctrl+PgDn to enlarge (or Ctrl+PgUp to shrink to normal size) and then Ctrl+G to add the grid. If you still need it enlarged, go to View>Zoom>Custom and bump it up to 600% or 800%
For sprites, head to
http://www.spriters-resource.com/, if you need mario, pick the game system you want to reference, like NES or SNES, and pick a game that you want to extrapolate him from. Right click the image and store the file in a place you can remember, such as My Pictures in a new folder called Sprites. Open MSPaint, File>Open and find your image. Enlarge the image, cut out the one u want. When the dotted line is where you want to crop the picture, press Ctrl+C to copy. Then go to File>New and press Ctrl+V to paste you new sprite. Follow the instructions at the top to enlarge the image and add the grid and presto! You are on your way to perlerizing mario.
Good luck
