You want to display a full HD video on you primary screen... at full 1080p. Only way to get it is to full screen the thing.
That *THEN* turns the other screen(s) into Grey backgrounds. not allowing you to and use them. Such as using a virtual box machine in the other window. Of doing to spreadsheetings or wordy docuemnty thingers... or even browsing the ENTARNETS...
Nope, just that one thing for you!