Niko,
Probably the latest ASCOM drivers for any guide scopes/ cameras etc.
Using CdC??
You mention a USB>serial adaptor - I therefore assume you won't be using a EQDir module to connect to the mount, but connecting through the hand controller.
You need to set the mount as a SW NEQ mount.....that's about it.
I use a usb to serial cable and Windows 8 and 8.1 just automatically install the drivers for it. However I did make sure I got one that said it was supported by Windows 8 as I'd heard of people having issues with usb to serial converters that used older chipsets.