No modern UAV has hardware capable of running an entire Windows installation.
I highly, highly doubt that you're right about this. If you happen to be right, you won't be for long. It might be that nobody wants to run Windows, but there is clear motivation, as well as hardware and software technology, to have a full-scale OS on an advanced UAV.
The google car is an exception where there is a lot of sophisticated software. UAV's like Boeing's and even the ones you buy online (with the open source software) are running on boards, not full-scale PC's with the ability to play a DVD.
UAVs are very complicated in terms of technology and engineering, but the hardware is simple because it's basically just running control loops on some board.
I highly, highly doubt that you're right about this. If you happen to be right, you won't be for long. It might be that nobody wants to run Windows, but there is clear motivation, as well as hardware and software technology, to have a full-scale OS on an advanced UAV.