Browser problems internet explorer

Question

Hi all,
recently I have placed a TV next to my PC to watch something when I am doing boring tasks that I can use as monitor by an HDMI cable.
When I use it as a monitor I can watch movies too, for example connecting to the RAI site that has a lot of recorded clip in streaming.
I have still a problem: when I open with explorer the RAI site (that uses silverlight) and I drag it to the 2° monitor (and keep firefox in the first monitor to navigate) and maximize the clip to full screen, when i go back to the first monitor and click somewhere the movie go back to a little dimension: in practice I can keep it at full screen only if I don't touch anything.
Does anyone know how can I fix this problem?
Thank you

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