FIXED FOR ME! Yeeehah! Finally.
I did all the other things and nothing made a difference - checked Direct X was up to date (it was) , re-installed my nVidia drivers completely. Plus all the other things. Anyway I run Windows 2008 Server R2, rather than Windows 7 or 8 because i am a developer, and then found this page:
http://www.win2008workstation.com/missing-xinput9_1_0dll/
Now i have used this site before because i have a server as a desktop machine, so i know that it is bug-free - i,e, no someone trying to put a trojan on my computer. I downloaded the file and run it (it installs a (missing) direct x dll on your machine) and now the damned game works!!!!!!!
The reason i had problems is because on the server OS those files are not installed at all.
There is also the issue of 32 bit (x86) and 64 bit (x64) versions of the file. If you have a 64 bit OS then you will probablty need both versions, and i could be wrong but i bet other people who have problems under windows 7 and vista are just having a version problem where one version is installed but both are needed.
Anyway i hope it helps 🙂
