There is no way without doing some programing, e.g.
ShowWindow Function (MSDN) or
Link Removed - Invalid URLLink Removed - Invalid URL.
Autohotkey (very easy to use, very popular):
n=0
!+t::
WinGetActiveTitle, T
if n=0
{
WinSet, Transparent, 222, %T%
n=1
Exit
}
WinSet, Transparent, Off, %T%
n=0
Exit
It'll make your active window semitransparent (or whatever value you set 0-255) when you press Alt-Shift-t. If the active window is already transparent, it'll make it opaque.