use bootcamp to install drivers on your usb ONLY.
reboot the computer
boot recovery hd partition. .Hold down option/alt before it turns on. the key right in the middle in control and command.
Format Drive To MBR-only in disk ulitiy Go to your hdd.It will say "Macintosh HD" Under that you see "Options" and you click that and click mbr disk or whatever.
put in your windows cd (if you can)
Reboot and Install Windows.Hold down option/alt before it turns on.Keep holding it until you see a menu.You can now put in your windows installation usb or disk if you didnt do it yet.If you dont see a cd saying Windows and EFI boot reboot it and do to same thing..Hold down option/alt before it turns on. If you do,you dont have to reboot.it is right in the middle in control and command.When your done,crate a partiton and install windows
Done.You now have windows installed,with bootcamp!