I know this is a late response, but if anyone needs any help in installing this driver for Windows Vista/ 7 64 bit, I found the proper driver. It says it's for Windows Server 2008, but I believe the kernels are based on the same things. Windows 7 Ultimate 64 Bit installed flawlessly on my Ultra320 SCSI drive in my Precision 670 and I needed no add-in cards.
The driver is here: http://www.adaptec.com/en-us/speed/scsi/windows/a320raid_win2k8_x64_b212_exe.htm
If this is the wrong place to put this reply, could you direct me to a better place to put this? I just figured that people who seek info on how to install this onto a 64 bit Vista/7 OS would want to find this bit of info and seeing only the 32 bit help here would frustrate them.