bryonhowley :
I do not think you can if what you are asking is replacing the UEFI BIOS with a legacy BIOS? That system was build for Windows 8 and UEFI and that is it.
If what you are asking is legacy support within the UEFI well if Acer did not provide that you are most likely out of luck there unless they release a update that adds it. But what exactly is missing that you need? There should be everything in the BIOS you need to run Windows 8 correctly.
thx for reply... i came across a problem that my gpu did not support UEFI system... theres alot of forum that i came to see that their problem same as me and solved by changing the UEFI to Legacy bios... i dont know how they change...but acer does have some guide to change or switch to legacy... unfortunately my bios feature does not the same as my bios and i dont see any option in bios for me to change it to legacy like others bios have... =/
UPDATE: ty for help... after a few weak of headache and research through forum... i managed to change it to legacy... problem solved!