The quick (and some way dirty) way is to take a picture of your window, then edit the image and crop it so you remove anything surrounding and keep the window only. Then you can use that cropped as a texture for a box which you have to stretch to the appropriate size for your window.
Of course the window glasses will not be transparent (they are just a picture) and the window frame itself will not reflect the light as it would do if it were the real thing.
The optimal solution is to create the model with some 3D modeling software, assigning the corresponding materials for each part.
Finally, as an intermediate solution, you can construct just some simple parts which together compose the frame and assign to each part the cropped corresponding part of the window picture you took, and then use a glass in the middle of the frame.
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If a long walk every day were healthy, mailmen would be immortal.
