Removing the window with ample force (e.g. sledge) would be easy. However doing it without destroying much of the surrounding wall is not so clear.
The aluminum frame is obviously connected with a flange which goes into the wall. Somehow this flange must be ripped out or cut from the rest of the frame.
I could envision a LOT of creative hacksaw work could do the job but that would require DAYS of work, since the frame would have to be cut thru every few inches.
No other saw I have could cut into the edge and any I can imagine which could cut through the aluminum would tear up the wall in the process.
I did a google search and thus far nothing came up. I imagine there are some techniques or tools used for this, because people replace old aluminum windows all the time, especially when damaged. How are the originals removed?