Use for old windows?

We are replacing six windows in our house that were installed wrong, and are causing leaks. I am trying to avoid putting stuff in the landfill, and was wondering if anyone knew of any alternatives for them? They are old vinyl windows, and I know Build It Green won’t take them. I’m not even sure if they could be used as windows again, but thought maybe there might be some other use for them, such as making cold-frames for the garden.
If anyone has any ideas I’d love to hear them.