Windows 10: Question About Going From Windows 10 Back to Windows 7

I plan on doing the same thing as Voyager1 with just a slight modification.
I have posted this question elsewhere as well, so sorry for the duplication.

Currently I dual-boot - Win7 Pro 64-bit (OEM) on one drive and WinXP Pro on another drive (using EasyBCD)
I have a spare drive and what I was planning on doing was clone my Win7 to it and then do a free Win10 upgrade on that cloned drive.
I would "test out" Win10 to see if I liked it while still using the Win7 on the other drive.
Because the cloned Win7 would have its license upgraded to a Win10 license, would I have any problems using the Win7 on the original drive?
More importantly, can I leave all 3 drives active in the machine while I do all of this?
Thanks.

 

Of course I have. I've used Acronis, EaseUS, and Macrium throughout the years, and now I use CrashPlan and SOS, two online solutions. However, a full system backup wouldn't have helped if it had been correct that taking advantage of the free Windows 10 upgrade offer invalidated the Windows 7 key, as per the speculation at the time. Now, of course, we know that not to be true, and a full system backup is a good way back to 7 since the 7 key will remain valid.

By the way, I tried Windows 10, and it's a pile of garbage. I don't like their forced Windows updates.

Lastly, regarding your "Backup! Backup! Backup! You'll be glad you did." signature, it should read "Back up! Back up! Back up!" A "backup" is what results from backing up your data. You want the verb form here (back up), not the noun (backup). Even online backup programs like SOS and CrashPlan can't get it right, so it's not surprising you cannot, either.