This is obviously with the old drive disconnected?
The the commandline function diskpart, and the /clean command will do the trick.
You can clean internal and external hard drives using the command prompt by following our instructions.
www.tomshardware.com
This article explains the Microsoft Diskpart Erase utility. The command that erases the drive during this process is "Clean". In this article "Clean" and erase are used interchangeably. Cleaning or erasing a storage device removes all data and partitions from the drive.
www.seagate.com
Follow these step-by-step instructions to perform a successful diskpart delete partition operation among other disk-related jobs in Windows.
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Be absolutely sure of which drive you're accessing.