将Xcode证书移动到iPhone开发的新系统

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.In Apple's Provisioning Portal "How To" under C