very carefully! plus, depending on if the window is exterior glazed,
1, remove (if you can) the black rubber seal from the opposite side to the beads.
2, close the window and push the unit back away from the beads, without the gasket in this should be relatively easy.
3, remove the beads with a small paint scraper or anything similar, remembering their position in the frame, side beads first, then remove the bottom bead, this should ensure that the unit wont fall towards you.
4, remove any packers that you can see then gently coax the unit out with a scraper or by gently pushing it.
5, reverse the process when glazing in the new unit.
carl, August 2010
