How To Assign a New Active HD in 8/1?

My active hard drive is failing and I want to assign another HD instead. How do I do this?

If your current HDD contains OS,download AOMEI Backupper and clone the active partition to the new (same or bigger sized) HDD and set it up via BIOS to boot from it.No need to assign the C-letter,if you are going to boot from the cloned HDD,its gonna be named C anyway.If its a data-containing HDD,a simple copy-paste should do the job just fine.