> Any way to selectively enable USB Devices?
Not really; the problem is unlikely to be the USB-attached devices, but an interaction with the host controller that provides the USB bus support itself. There are some hard things to deal with with these drivers, especially in the presence of things such as BIOS built-in USB support for some devices (smooth transitions from a BIOS driver to a full OS driver are difficult).
> If I enable the -NOUSB option how can I backup to a USB HardDrive or use a USB Mouse?
With Ghost's built-in USB driver, you can't. With an external USB driver, possibly; if your BIOS directly supports these things (some do), or if you have a DOS driver for these devices, you can use them with Ghost because the -nousb switch just affects Ghost's internal USB driver.
Similarly, if you have a 32-bit version of Ghost that can run on Windows PE, the USB support in Windows PE takes over - there isn't a built-in USB driver in Ghost32.exe