dell 4600 bios not allowing windows 8 upgrade due to bios security setting

there is a lot  of talk about this i went to dell no bios upgrade for 4600 already upgraded to r12or a12.downloaded upgrade for 4700 popup says no way .will not allow .put it on a floppy disk to load from boot unreadable. any more help want to go to windows 8 $69 at staples no fun yet Ed