This leads to a simple question – what operating system are you using? I've been using Windows XP for 15 years (and wrote everything for it), and it only had Service Pack 3 officially, with Service Pack 4 being just a collection of all subsequent updates. I know that later versions of Windows sometimes have problems installing "older" games.
Windows sometimes has glitches where it suddenly starts requiring additional software for installation, even though it didn't require it before and won't require it later.
Licensed Win 8 Enterprise Edition (a legitimate copy from work, which I installed at home).
