Other reader who may be trying to use iSight drivers to connect an external iSight to Windows on a PC instead of a Mac will likely find it easier to use a different webcam designed for PCs. In fact, these same iSight drivers work regardless of how you are running Windows on a Mac, whether from BootCamp, Parallels, VMWare Fusion, VirtualBox, or other method. This is true even when you are using VirtualBox to run Windows on your Mac.
Whether your Mac uses a built-in (USB) iSight or an external (Firewire) iSight, the drivers you should use for Windows are always the same one furnished for use with Boot Camp. Go to the WindowsSupport folder on your USB drive.
Plug the USB drive into your Windows machine. You can find help for those specifics in In the Action menu choose Download Windows Support Software and save it on a USB drive. How to find and access the specific driver version for your system depends on which specific Mac, MacOS, and Windows version you use. You may also use the CD/DVD that came with the 24-inch Apply Cinema Display for the Windows 7 or 8 drivers. If you do not have the system software disks, you may need to buy replacements for the correct disk(s) for your Mac from your Apple Retailer. If Windows 8.1 drivers are not available, then you may download and install the available Windows 7 or 8 drivers and install it in its compatibility mode and check if that helps. The drivers that Apple provides for use with Boot Camp are the only source. Is there a driver for the isight windows except the one in bootcamp.