I'm not sure.
I guess that in "Device Management" you can uninstall the IDE controller. (But please, be sure that you don't uninstall the controller where the boot disk is).
Next time you boot Windows will find new hardware...

Or maybe just changing the driver of the IDE controller in its properties...

Anyway, try to find the SiS driver and disable it. (Maybe Feurio "System Diagnosis" can help you).