You can in windows paint program.
Open the file with paint. Select what ever you want to copy or move and click on the bottom left side box (sorry don't know what its called?) it will erase anything white so now you can move your grid over the map.
THIS IS PAINTS HELP
"To specify transparent or opaque drawing
To specify transparent drawing, click the Image menu, and then clear the check mark next to Draw Opaque. This specifies that the existing picture will show through your selection and that the background color of the selection will not appear.
To specify opaque drawing, click Draw Opaque. This specifies that your selection will cover the existing picture, using the foreground and background colors of the selected object."
Pokie