It sounds like a software issue in Windows, since it's working OK in Ubuntu. I don't know if this will help:
http://rog.asus.com/forum/showthread.php?5524-More-Accurate-2-Finger-Vertical-Scrolling-with-Touchpa...But give it a try and let us know...
If it doesn't resolve your issue, I'd be tempted to uninstall the current Synaptics driver (you are SURE you have a Synaptics touchpad, aren't you?), reboot into Safe Mode, use Driver Sweeper to remove any detected Synaptics driver remnants (possibly even use CCleaner to clean up the registry), then install the correct touchpad driver (from Safe Mode) and reboot. Installing the driver from Safe Mode will disable other running drivers that may potentially interfere with your touchpad driver installation.
G74SX-A1 - stock hardware - BIOS 202 - 2nd Monitor VISIO VF551XVT