you can do it through the BIOS. While the PC boots, look for the message "press F1 to enter setup". The key may change form mobo to mobo, but it's generally F1 or Del. you cannot (or shouldn't even if you can) disable it completely unless you have dedicated graphics card, you can only reduce it.
after you enter setup it is generally in advanced. don't change anything in the BIOS unless you know exactly what it is.