The only reason too big is an issue is because you may not be able to format a 120GB drive to FAT32, thus the BIOS program may not be able to read it or the BIOS file on it. Windows cannot format a volume that size to FAT32, it must use NTFS which BIOS may not be able to read. With an 8GB flash drive you should be able to use Windows explorer to format (right click, format) the flash drive to FAT32 no problem. I have a dedicated cheap FAT43 4GB flash drive at work that is used solely for BIOS updates. The port you choose doesn't matter but back ports near the ports in the back of the PC are ideal.