Moving Xcode certificate to new system for iPhone Dev

In Apple's Provisioning Portal "How To" under Certificates, there is a section called "Saving your Private Key and Transferring to other Systems". Now this is what I'm doing (I have rebuilt my machine with a new HDD and therefore have access to my previous OS build) and I'm looking to backup my private key so I can install it on my new OS build and start codesigning iPhone Applications again.

The problem is, in the how to, it says to backup the "<First Name> <Last Name> public certificate that is paired with it." (although the image is a private key):

And so when I checked my KeyChain, I've found 9 Private keys and 9 Public keys with my name on, so how do I know what I'm looking for?

I found in the first private key, it has this access control:

But when importing this I get a message saying it cannot import :(

So really, I just want to know which one I need to import - I guess I can try trial and error with them but would like to know either way.

You click on the small triangle at the left of the key and the one that has "iPhone Developer:"First Name" "Last Name" as a child is the one you want.

BTW, it's Xcode, not xCode :-).