Hi ice-coffee123,
I am Dave, I will help you with this.
1
What method did you use to delete the Windows partition on the old drive and did you only delete the C drive partition.
2
Was there a separate partition on the old drive that contained data that was encrypted with Bitlocker and now the whole drive is now marked as unallocated with no partitions showing?
Do you have another PC you can connect the old drive up to to see if the other partition is showing on that PC?