I am considering pulling out some windows and re-using them in another area... BUT.... buggered if I can work out how to get them out!
They are what I think are referred to as vinyl frames... they look like painted aluminium, but some googling suggests they may actually be some sort of hard PVC. They are generally used in colourbond sheds, if that helps anyone... (not sure if you have that over in the UK, but Nev will know what I am on about, I think, and may be able to translate

I can see no screws whatsoever, and am beginning to think they are somehow just glued into the frame. I can see slight signs of a brown substance on the inside sill, and on the outside I can see silastic under the trim. Is it possible the windows could just sit in the sill with glue???

Sites I have checked suggest vinyl windows are installed with 2 screws in the centre of the uprights, but there are definately none to found.
If this is the case, what are the chances of removing and reusing these windows? Has anyone done this? Am thinking I could try butting them out from the inside with a block of wood and a rubber mallet, but am not sure the glue will give and am afraid I may twist them. They are very tight and any attempt to slide something between the window and the frame would probably damage it, I think. I can't see any other way though... Am I missing something here?