Windows 10: Transfer Win 10 (free upgrade from win 8) to a new hard drive

I'm upgrading my brothers PC from a decently bad OEM computer, but as recompense, I'm taking his 1 tb drive, and I want to transfer everything to a 320gb drive. However, the windows 10 on his computer is from the free upgrade promotion a while back, the computer originally had windows 8, so I do not have a key to activate windows with. What do I do to transfer the drive fully?

:)

 

New Hard drive. Awating delivery of new OS (was originally Win 8 but was upgraded to Win 10.

My hard drive died on my old computer this week and I replaced it. went looking for original recovery discs (was Win 8, upgraded later to Win 10 on insiders preview). Ordered new Win 8 discs with intent to upgrade to Windows 10. What will happen if I don't
get the discs before July 29th?

 

Transferring old Hard Drive to New Computer. Is it possible?

Windows 10 is still a free upgrade if your on win 8 or 7 and yes if its a sata drive you can move the Hard drive over to a new computer but the operating system will not work.

 

Installing the Win 10 upgrade on a new hard drive

My current hard drive is really old and unstable, and I've planning to buy a new SSD for my computer. When I get the Win 10 files, will there be an option to install it on the brand new SSD without changing anything on the old hard drive? My understanding
is that Win 10 will allow installing on a new partition on the drive where the current Windows system is installed, and it will also allow creating media for installing Win 10 at a later time, but it is not clear if the upgrade will allow keeping the current
system and hard drive as is, and clean-installing on a brand new hard drive.