Aliminium window come off rails and stuck

Hello,

The aluminium window in one of my bedrooms has come off its rails, and is now properly stuck

I've tried, with increasing amount of force, to move it in either direction. I've also tried to use a mallet to push it back onto the rails. No luck

Any help with fixing this would be appreciated. Pictures following;

20160726_051216 (Large).jpg 20160726_051230 (Large).jpg 20160726_051239 (Large).jpg 20160726_051248 (Large).jpg
Attached Images

http://www.renovateforum.com/images/attach/jpg.gif 20160726_051216 (Large).jpg (447.3 KB)
http://www.renovateforum.com/images/attach/jpg.gif 20160726_051230 (Large).jpg (535.0 KB)
http://www.renovateforum.com/images/attach/jpg.gif 20160726_051239 (Large).jpg (588.1 KB)
http://www.renovateforum.com/images/attach/jpg.gif 20160726_051248 (Large).jpg (468.1 KB)

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