I have a 13 inch Macbook - Late 2009. I am running Mountain Lion 10.8.4.
So I downloaded the Windows 7 img from my university's website and then converted it to iso and tried:
1. putting onto USB
2. burning to DVD
Both times gave the same results.
I have the latest Windows Support Drivers on a different USB. After I partitioned and my Macbook reboots, I get stuck when it says it can't find the necessary drivers in order to complete the installation. I never actually load the desktop to Windows 7 because I can never get past this step.