Question about disc drive lettering and key change

I have a new laptop which had OEM 8.1 on it.
The installation backup is held on a partition labelled 'D'.
I split the main partition and for software reasons need the new partition to be labelled 'D'.
If I change the drive letter of the backup partition is that likely to cause me problems later if I have to restore the installation for any reason?

ALSO

I used the 'add features' option to upgrade the license from OEM Home to Pro.
When I did this I was required to re-activate as the key had been used on my previous laptop (which died - RIP).

However when I use a script in CMD to view the key, it is a totally different number to the one I entered.

My intention is to later upgrade to Win10, then do a complete fresh install of 10, but I am now wondering if the key I already have will work with the Win10 install as it appears the key now registered in my system is different.

Any clarification would be appreciated.

I think I've found the answer (can't change it without causing a problem) but what is going on here - it shows twice in Disk Management

If you use a third party backup program like Macrium Reflect, it wouldn't matter where the backup file is at.

Try showkey, option six here, http://www.eightforums.com/tutorials/27129-product-key-find-windows-8-a.html. It will list your OEM key and the Pro key. The OEM key will be in the BIOS and the Pro key in the Windows Registry. Your factory recovery may already be non functional. The partition is still there but the link to it from the hotkey you press on boot up may be broken. It's not so much the drive letter change that messes things up, its the actual partition number. Changing the disk structure/layout can mess it up. There are some here than can get it working again. I don't have those skills, not yet anyway. KYHI can likey help you out though. Just send him a PM.

Thanks alphanumeric.

That answers my query about the keys.

The backup should still be ok as I haven't changed any drives or details - will do a clone of the drive and a clean install of Win 10 in due course - so the backup drive can go then.