Basically, you are looking for an utility, which will help you to open up bios and translate it yourself?
Such programs do exist for some
BIOS vendors. But problem is, that there are some many vendors and versions of firmwares that it is not possible to create a universal editor. And most of those firmware are available only in English versions.
There will be no visible reaction of Windows 7 to a new BIOS, whether officially patched or not offically (if your won't brick your computer of course and it will start).
There used to be a custom patcher for BIOS firmwares, that allowed motherboards to recognize bigger hard drives. Those things were totally home made and Windows run smothly on those computers with non-orginal firmwares.
Changing bios - whether that is it's language, ability to read bigger HDDs, SLIC information or some other information in it, will take no affect on language of Windows itself
(menus & help files).
Language feature of Windows 7 is independent. You would have to have Windows 7 Ultimate, Enterprise (for corporations only) where you can legally change Windows language yourself, but that feature is not auto-configuring (you have to manually select it
and download some Language Interface Pack [LIP] files).