The truth is that you do need to re-activate QuarkXPress if you change the hardware of your computer. In order to avoid the hassle of a phone activation, you should de-activate Quark before your machine undergoes motherboard change, harddrive change or other surgical intervention.
This option is available since version 7.02, it is named "Transfer licence", and you find it in the QuarkXPress menu (Mac OSX) or in the Help menu (Windows).
Manuel S.
Technical Support Representative