If you're using Western Digital HDDs, they give away a copy of Acronis imaging software. The catch is, it will only work with WD drives.
So, you image the Windows 7 drive, to a blank WD HDD. Then just put it away, along with the serial #, in case you need to activate it later, should that become necessary, (You want to return to windows 7).
Then just install Win 10 in the upgrade mode on the drive you're using now.
BTW, where did you come up with the copy of Windows 7 you're using now?. I of course don't really care, but it would have to be a legitimate copy, so that M$ would reactivate it at a later date.
FWIW, every version of CCleaner I have run across, has worked with Windows 7. I don't particularly care for the live monitoring new versions, so I run an older version.