Philip,
There will be 2 drivers for the camera, one is the windows drivers so windows can see the camera and the other will be the ascom driver so ascom can talk to the windows driver which in turn talks to the camera. I suggest installing the windows driver so windows can see the camera and connect PHD to it using the WDM option in PHD and see what the the maximum exposure time you can get from the camera. I normally use 3 second exposures for guide cameras. Look for PHD here ->
http://www.zwoptical.com/Eng/Cameras...are_others.asp If you can only get like .1sec exposures you won;t see many guide stars from the camera.
If the WDM driver will not let you do 3 second exposures then I'd look at installing the ascom driver and see if you can get longer exposures from that setup. You will have to download and install ascom 6.1 before installing the camera ascom driver or you'll have issues with it. Use PHD to connect to the camera but this time select an ascom camera and yours should be in the list.
If you don't need ascom then a GPUSB is definitely an option. It will connect your PC via usb and to your mounts guide port for guiding. Alternately you can use ascom and eqmod to talk to your mount from the PC and use that to send guide pulses to the mount. This is called pulse guiding and you don;t need a guide cable. Less cables on the mount is always good.
To get eqmod to work you either connect from a serial port to the cable that came with the mount plugged to the handset and put the handset in PC DIRECT mode to get a direct connection from the the PC to the mount. A usb to serial device can be used here for the serial port. The handset in this mode does nothing at all, all control is via the PC
Alternately you can buy an eqmod cable which can connect directly from a usb port to your mount, replacing the handset completely. Mine has been in a plastic bag in the parts box for a couple of years
I'm sure bintel sells these cables but I can't find them just now. Eqmod is the name of the skywatcher mount ascom driver. It's a community affair and works quite well.