The main question is this. Does you TV get recognized as a seperate source on your Video Card?
Right click on your desktop>Properties>Settings. Click Identify and see if both your desktop and your TV have the same output. If they both read the same output # you cant do it. But if your TV is Identified as #2 while your Monitor is Identified as #1 you might be able to do it.
But you will have to do it from within your dads account. Have him log in. Run the movie and move it to the TV (Assuming it is recognized as a seperate source). Then you dad can continue to work.
Be warned as this will eat up a lot of processing power. So if you dad has anything Graphically challenging to do your movie and his work will lag.
I do not accept support questions via EMail, PM, IM or my G+ page!
Phone: LG Optimus G Pro
Running: Stock JB from LG with Nova Launcher