Hi folks thanks to mvallevand I have the final version for my script:
!^y::
WinSet, Transparent, 250, nPVR
return
!^t::
WinSet, Transparent, 129, nPVR
return
!^b::
WinSet, Style, ^0xC40000, nPVR
return
control+alt+t: will display a nPVR transparent window
control+alt+y: will display a nPVR non-transparent window
control+alt+b: will show/hide the border including minimize, maximize, close buttons
you can change the 129 value to increase or decrease the transparency a lower value to make it even more transparent.