Pictures show the careful removal of sash and bi-folding windows. For the sash windows, the window surround (architrave and lining) is first removed, then the nails holding the frame are sawn through before removal of the whole window. For the bi-folding window, the lower steel runner within the sill is first extracted (Steps 2 and 3), before the window can be removed, leaving the frame intact.

Sash Windows - Step 1	Step 2
Bi-fold Windows - Step 1
Step 2	Step 3	Step 4