Blue screen while installing Boot Camp support software in Win7 Ultimate x64

2012 macbook pro with OSX Mavericks. Installing Win7 ultimate x64 using boot camp assistant and a USB drive went flawlessly. Then I downloaded and installed the boot camp support software from support.apple.com/kb/DL1638

Running setup.exe bluescreens my computer and makes the windows partition unbootable after that, even in safe mode. I performed a system restore to roll back the boot camp software and booted again, and checked the log file. It pointed to an intel USB driver. I then deleted IntelxHCI from the Drivers/Intel folder, ran setup.exe again, and everything installed perfectly.

My question is: what is the Intel usb 3 extensible host controller, why is it included in the support software, and why does it immediately brick my Windows partition?