Unstick a Window

Take It Outside

If this still doesn't free the sash, you may have to attack the problem from the window's exterior. Assuming the window is accessible and not four stories up, gently wedge a pry bar under the sill along the corner of the window. You may need to tap it with a hammer to get it in place.

Stick the block of wood under the pry bar so you don't mar the sill. Using the leverage of the pry bar, try lifting the sash -- working it evenly from one corner to the other to prevent damage to the window.