well kboy you CAN do a full install with an upgrade CD, this is the point we're trying to make.
apokalipse what he meant was that doing an upgrade over a previous operating system, like win98 to win2k, is not as good as doing a fresh install where your drive is formatted and you install everything fresh.
upgrading over a previous OS can cause your system to be unstable. for example when you upgrade the registry becomes filled with old entries from your old operating system. sometimes old settings interfere with the new OS.
other reasons being that some things might not work right, your OS becomes corrupt or unstable, you might end up with old unused files cluttering up your OS partition or even extra files and folders, .......that sort of thing