I've having the same nightmare as mentioned above. Read tons of posts over the past 2 days with loads of reboots, reformatting, etc....& still no keyboard (apple wireless or windows usb) or mouse to get past the windows language preference page.
I had a break through 1 hour ago using various advice online.
-windows 7 64 bit ultimate as an ISO pre-prepared and on my iMac 27in desktop (although this probably wasn't needed since I used the original DVD exe installer disc as the windows boot instead. But has been included as it was actually still there from previous install attempts).
-usb 2.0 64gb MyMemory stick in slot on left hand side as I look straight at the screen (closest to thunderbolt slots further left again as I look straight at the screen), . There are 4 usb slots on the back of this iMac.
-slot 2 has a usb unpowered hub to give me 4 additioanl usb slots (although it uses 1 of the main ones). I plugged my mouse & windows keyboard into the hub since they are low power users.
-slots 3 & 4 on the back of the mac screen were taken up with an external samsung DVD writer. An original windows 7 64 bit DVD was in the drive.
-I started the iMac. Opened the Boot Camp Installer. Formatted the Mac drive to 1 single drive...for the last time
-restarted Boot Camp. Ticked all 3 boxes. Split the drive 50/50.Other normal procedures/passwords continued.
-when it finally rebooted it went straight it went straight to the DVD and into windows install (no Alt press down required)...and the windows keyboard finally allowed me to use the arrow & tab keys to load up windows.....HOO RA.
-193 important & 43 optional updates for the next stage of this tooth pulling exercise of windows installation!
I really hope that this helps some people to finally get past this problem keyboard/mouse problem
Best of luck.