Are there computers that can only run windows 8???

hi guys just want to check

i bought an acer veriton e430 preinstalled with windows 8 (which i dont want to run)
in the bios i have disabled secure boot
there is an option for hard drive operation ahci or compatible
and i have changed the boot order to
cd/dvd
hdd
etc

there is no option in the bios to change from eufi to legacy like i have done on some machines.
the options just dont seem to be there....maybe a bios update???

but it just boots straight to 8...if i select boot options only windows loader is available, no optical disk...

are there some machines that cannot have any other os loaded except 8...what if i want to duel boot with linux???
this is crazy!!!

any help appreciated