Boot Camp x64 is not supported on this computer model

Hello All,

I need some help installing Windows 7 on my imac I have listed all of the specifications here:

24" iMac - Early 2009 - Intel Core 2 duo E8135 - 8 GB - running El Capitan

I have several versions of windows that I can install:

XP Pro, Vista (somewhere), Windows 7 upgrade 32 bit version, Windows 7 full install 64 bit version

The problem that I'm having is that while I was able to install the full version of Windows 7 (64 bit), I am unable to find any version of the Boot Camp support software that will install correctly. When I try to install the software that downloaded when I created my PC partition in boot camp it gives me the message "boot camp x64 is not supported on this computer model."

Does this mean that I can only have a windows partition that will run correctly if I purchase a 32 bit version of Windows 7? Is there any way around this, such as installing Snow Leopard first on my mac, and the corresponding version of boot camp. I suppose I could start there and do all of the upgrades?

Thanks in advance for your help!