Acer aspire wont boot CD/DVD


Jan 12, 2015
My laptop model is acer aspire 5742G

Basically I want to install windows 8 on it,I tried to boot the windows DVD from the boot menu yet it wasn't one of the bootable options,So I went to the setup menu and changed the priorty (bad english sorry) and made the USB CD/DVD the 1st option in the boot menu,I saved the options and the laptop restarted ,Then I went on the boot menu by pressing F12,Yet I still couldn't find the
CD/DVD as a boot option,All the options availabe are 1.Netword boot,2.IDE 0:ST975042AS,3.IDE1:HL-DT-STDVDRAM GT32N

Thanks in advance ~