You know what, the problem has been fixed. I finally musterd up my courage and reinstalled Windows 8.1. The game is now installing. Thanks for your time though!

Well yeah, the "latest" installer still looks for WMP.

Am I supposed to download a file called "GTAV_Setup_Tool.exe"? If I am, then this is really absurd because the error is exactly the same! It's still stupidly trying to look for WMP.

I'll see if there are any more answers, and if there aren't in the next few days I'll just mark your answer as accepted.

Yeah well apparently the retail copies won't be recalled, and we have to keep looking for the solution. Great, thank you Rockstar.

My copy of Windows is Windows 7 Ultimate, and this version has WMP. But for some weird reason it's not installing. I think if Windows 7 N and KN versions don't have WMP then it shouldn't appear in the Windows Features. But mine has. So that's the weird part.

@RossRidge You're right, my copy of TWD does not have Steam listed as a requirement. However, and not sure if this helps anything at all, there is a small 7-digit code printed at the lower left corner of a booklet. Does it mean anything?

The cashier opens the case for everyone who buys a game. She was also as confused as I did.

I don't think so, I bought it from a store which I have bought many other games from that have working CD keys.