The driver DVD supplied would have been made months before Windows 8 was released, but you should be able to download Windows 8 drivers from GigaByte's website. You'll need to know the full model number and revision number of your motherboard as there are over two dozen boards in the UD3H series: http://www.gigabyte.com/support-downloads/download-center.aspx?kw=ud3h&ck=2#1
I know for a fact they have Windows 8 drivers for some UD3H boards 'cos i just checked. Hopefully yours is one of them.
The full model number & revision number of your board should be printed on it, on the populated side.