I just bought and tried to install GTA IV onto my computer which has WIndows 8.1. It started to install (and seemed to finish) but then said,
"Your System is incompatible with %P.
Please follow the link below for more information."
The only thing below is a Microsoft logo and the "Finish" button. If the Logo is the link then it doesn't work. I am also 100% sure that I have exceeded the system requirements (If those are relevant to your answer then just ask for them).
The game is new, not refurbished.
It is also a Game for Windows Live, which I've heard may be the problem.