Kobe Eveleigh :
I can't remember if it might have been an upgrade though the free uograde program. It either had 10 or maybe 7 pre-installed. It runs but we stopped using it since it was slow even for browsing. Can't remember 100% because we had an old budget model, used this for a little while then replaced again for an iMac, we just use it as an internet/ office PC. We either upgraded the old old one or this 2015 model.
EDIT: Confirmed that the 2015 desktop is a free upgrade
OK then...
If it runs, do the stuff in here:
https://support.microsoft.com/en-us/help/20530/windows-10-reactivating-after-hardware-change
http://www.tomshardware.com/forum/id-3164428/windows-build-1607-activation.html
This will link that digital entitlement to your MS account.
Later, on the new hardware, you can transfer that digital license over, and activate it on teh new hardware.
Obviously, only one system at a time.