Your Mac is one of those that is not supported by 64-bit Windows.
http://manuals.info.apple.com/en_US/boot_camp_install-setup_10.7.pdf
create a Windows support software (drivers) CD or USB storage media
http://support.apple.com/kb/HT4407
The Boot Camp Assistant can burn Boot Camp software (drivers) to a DVD or copy it to a USB storage device, such as a flash drive or hard drive. These are the only media you can use to install Boot Camp software.
https://support.apple.com/kb/HT4569
Installation Guide Instructions for all features and settings.
Boot Camp 4.0 FAQ Get answers to commonly asked Boot Camp questions.
Windows 7 FAQ Answers to commonly asked Windows 7 questions.
http://www.apple.com/support/bootcamp/
Macs that work with 64-bit editions of Microsoft Windows Vista and Windows 7
Some computers require Microsoft Windows 7
http://support.apple.com/kb/HT4410
http://support.apple.com/kb/HT1899
FAQ: http://support.apple.com/kb/HT3986