it is very easy mate, just download the full trial version of nav2005, extract the contents, then you will have the retail version. after that, simply run your keygen and put the installation serial number, then activate by phone, get the challenge number, etc. etc. you don't need a crack for this. cracks contain trojans, spywares, etc.... so who will guarantee that you don't get these if you don't have a working AV in the first place? ( i know you will argue how to extract the files from a trial version to make it retails :P )
good link though, nice tip for all others who wish to get the software for free.