Seems to me like you may have found an older driver for your sata controller. I hate to recommend this but it might be a bios issue if they are all on 1 sata controller you shouldn't be seeing some of the drives. I also think you found an older (vista) driver not a windows 7 driver because Gigabyte hasn't released an official Windows 7 driver. Check out your bios revision, sometimes that helps. DO NOT ATTEMPT TO UPDATE YOUR BIOS HOWEVER unless you are fully aware of exact instructions how to do it.
Compare your bios revision with this:
GA-8I945PL-G - GIGABYTE - Support&Download - Motherboard - BIOS
Also try this for the driver installation:
http://america.giga-byte.com/FileLis...pset_intel.exe - Its windows Vista but it may work, I don't know which one you're attempting to install but this seems the most compatible.
If I understand correctly, when you first start your computer, your DVD and second HDD are NOT detected by Windows 7 but after you refresh in Device manager, it shows up?