I have double hung vinyl windows and one crashed open when I unlocked and opened it. The top came crashing down and now the 2 panes are inverted. I cannot pull the top window up past the lower one (which is now above it). Any suggestions? It is cold here...

Surly you realize that if the top sash came crashing down the counter balance mechanism is broken.

Look to see what is preventing the sashes from passing one another. If it is the latching mechanism remove it and raise the upper sash. If it is the weather stripping between the sashes remove the lower sash and push the upper one back up.

All windows I have seen have some way to remove sashes. Just how will depend on how it is made. If the lower sash tilts out for cleaning, unlatch, tilt out and push upper sash up.