you will have to download the software named @bios ,install it
http://www.gigabyte.com/MicroSite/121/tech_a_bios.htm
download bios update from mobos site
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http://www.gigabyte.in/products/product-page.aspx?pid=4150#bios
ok then you will get 3 files ,only .f15 file is important it will be of higher size, other two files named Autoexe and FLASH file are not important.
now open the @bios software - select update bios from file- locate the that imp file- select it - and click on update
it will finish in few minutes and ask for a restart. during update donot close or shut down pc.