In my humble opinion you are screwed. I would suggest two similar courses of action.
Burn a brand new copy of the Windows version you want to use and make a clean format/install of the above OS. Then you can register with your key if you still feel like doing so.
Another way to go, that works well for me, is to run a Linux distro on a USB drive. This way you are able to plug in an internet cable (since you have no drivers installed) and then download windows drivers manually and any other MS product you want. Additionally you can use Brasero burner or any other tool you are familiar with to burn the OS image. Then perform the procedure described above, by installing a clean version of your preferred OS.
I didn't got your question quite well, so my answer could be a bit vague or off-topic. Please let me know in case i can still help you.