If you try to install Windows 7 on a Zotac BI323, you will find that you have to slipstream the xHCI drivers in the installation media before being able to access the hard drive and install the system. This is covered in an article by Zotac, and worked well for me. The utility provided does not even pollute your PC with unwanted install procedures.
After having prepared your installation media this way, you run it and eventually arrive to the final install stage, where unfortunately it freezes at the very final “Completing Installation” step. At least, it did it with my otherwise very well tested Italian Windows 7 sp1 ISO.
At first I thought it could be something related to the xHCI drivers injected for this machine. But thinking more deeply about it, it turned out to be the WiFi/Bluetooth mini PCIe card. Probably, some driver provided in the ISO was not handling it properly. It was enough to disconnect it temporarily from the motherboard, install the OS, that reconnect it. Now you can boot regularly the just installed OS. You find the usual unknown devices, but now can comfortably install the drivers for them.