New HDD - does it need attebntion?

I have a new HDD to put into an external case. At present it can't be 'seen' in My Computer. Using a known good drive, all is well.
Does a new disk need to be formatted? If so how to do it.
I did wonder about connecting it internally which would be fairly simple.
Is there any other way of testing a HDD? It is always possible that the drive is faulty.
Another point. I notice that when both my external drives are connected, only one is 'seen'. My older HDD caddy is using USB but it can also use Firewire. Should I try that?

docusk

 

The hard drive probably needs to be formatted. Go to Run and type in diskmgmt.msc. It should show up in there. Right click on Disk n for the new one and do initialize. Once that's done right click on the window to the right and pick Partition (one partition is fine). Then when that's done right click again and Format. It takes a while to run.