1987 Windsor Windcheater

I have a cracked sliding window that I need to get repaired, The window is the large 1 beside the bed which has rounded corners, and is the slider not the fixed window. I have tried lifting the window to try and get it above the window frame so that I can take it out, but it will not lift high enough. I have phoned Windsor, who have no idea as to how to take the window out. I have phoned Camec, who told me that they make the windows but do not install them and do not know how to take it out.
Does anybody know how to take it out.