See the link below. Flash by USB or floppy (USB preferably). Always use a DOS Flash method, flashing with a Windows based BIOS live update utility is not recommended. Before flashing restore setup defaults. After flashing let the computer do a full reboot. Then shut the computer down and remove the CMOS battery to clear the bios. Refer to your user manual for flashing details.
"I read that it's risky , in which way? and what are the results of a failed flash? "
There is always risk involved when flashing the bios but sometimes is necessary and it's nothing to be afraid of. Just continue doing what your doing, getting advice and you'll be okay.