Moving Public and Private Keys IN PGP Desktop.

 If it is only your key you need, you can right click on your key in PGP Desktop, select Export, making sure that you then make the selection to include the private key in the export, and then save the key to your desired location.  On the new machine, double click on the key to start the import of it.  You will then need to right click on the imported key in PGP Desktop, select Properties and set Trust to Implicit.