You can run a new key, from MS in the installation.
But it must relate exactly to the Windows version that you are installing.
This information should be on the original disc or missing sticker, also within Windows !!
The UBCD keyfinder, should find your installed key, unless it has already been removed (by all this corruption)
It is also extremely likely that you will need to re-activate, and you may be given 3 days to do so. Therefore doing all this work without a valid key, would be a waste of time.
Have you given Ubuntu any thought ? Ubuntu is 100% free to private users, and does not have the activation issues of MS.
Also Ubuntu does Everything that Windows does (Internat; Mail; Word; Pictures; Media Player; Games except flash)
If you are wise at this point in your computers life, it would be better to go for this. You can even download the entire operating system. Also Ubuntu is way safer than MS Windows, usually it will never see Trojans and Virus.
Please put some thought into this, as I am concerned that you are trying to cut corners and this can be long road, to ongoing issues. Take this as your best advice, and act on it.