Re: Removing it
Standard version of Windows will not work.
Because it usually lacks specific drivers for the network and video cards used in the machine; I've seen that with just about any Windows version I've had to deal with. Which is solvable without having to buy another version: just add the network driver from an USB stick, tell Windows to update itself and some eleventeen billion reboots later you're left with just a few question marks in the device mangler, the drivers for which you have to scrounge from elsewhere. And anyway, you have a COA already, no need to buy a new install kit.
Or install Linux. I've had way less hassle there, if at all, over the past ten years or so compared to Windows.