i just face the same problem.. and this might be solution. 

i use macbook pro late 2011 and install windows 8.1. 

(prepare your USB min. 4GB)

1. ensure you download the windows support software from apple bootcamp.
2. you will get windows support folder in the usb. 
3. restart to windows
4. open your usb file there.. 
5. you will find setup.exe
6. right click on your setup.exe
7. go to compability tab
8. check the box of Run this program in compability mode for (and change the list to windows 8)
9. apply
10. right click again on setup.exe
11. run as administrator
12. and click. run the program without getting help. 
13. installing
14. restart
15. and voilaaa... all works