How to wipe old hard drive after cloning to new WD RE4 Enterprise

I have just newbe upgraded to a larger internal hard drive and successfully cloned the old 750GB drive to a new WD 2TB drive(WD2003FYYS). I wanted to use Acronis driveCleanser to wipe the old drive but I can’t manage to connect both drives to my tower at the same time.
The old and new drive both have the same copy of windows 10. After I select which drive to boot from I think WIN10 is automatically changing the boot sequence back to the old drive. I read to uncheck “Fast Startup” but that has not helped.
I have also tried switching the SATA port1 with the new WD drive. Am I missing a step?

Maybe I need to use an external HD mount and connect via USB or is it I just can’t use the same tower. The old drive will make great storage location for videos.

Thank you for any ideas you have,

eMachines ET1331G 64bit.
AMD 2.7GHz
6GB ram
WIN10 upgrade from WIN7 home

Hi, the easiest way is to connect the drive using a USB to SATA connection, you don’t need a complete enclosure, a simple USB to SATA cable should work just fine.