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#11
Why do you want to go back to 7 anyway?
You can pretty much configure Windows 8.1 to be same as Windows 7, it is smoother, better driver support, easy to reinstall etc., and it will not cost you anything.
Reverting bios to an older version is a bad plan.
If you need to run Windows 7 to run specific apps, then simply install it in a virtual machine. You still need a new licence.