W7 install disks are COMPLETE, that is when done, you will have the full W7 version you purchased.
'Complete' though could mean different things? Complete with your old programs and settings retained or a new complete install? Vista is the ONLY supported UPGRADE on the UPGRADE CD's MS sells. Even then, you have the choice of a 'completely' new install or an install over and retain the Vista settings and customizations as well as installed programs.
I believe in the distant past MS used to sell UPGRADE and FULL versions of the OS. UPGRADE versions would 'convert' the old OS to the new one. You could not use the UPGRADE on a new system or hard disk, a prior OS must be installed first for those CD's to work. This is NOT the case with W7 CD's.