I'm not sure exactly where you are having a problem: whether you can't download it, it won't install, it will install but you can't unlock it, etc..  The easiest way to ensure you can always get Qimage is to do what the registration email asks: save or print that email.  With that email, you have full instructions on how to install Qimage from scratch, even if you have a new computer.  Even if you need a new unlock code (because the one you have is too old), you can just go to "Support" from the Qimage homepage and then click "Request Updated Unlock Code" and you'll have everything you need to request a new registration email: it's all in that email you saved/printed.

Mike