I tried 2007, it gives the option to retain older versions if required and I kept Word 2003 and installed a few of the 2007 programs so I had both installed at the same time. However I didn't like 2007 and its incompatibilities with 2003 (which is what most of my colleagues use and the one we use at work) so I uninstalled it. Not sure whether installing the older 2003 will give you the option to keep the newer 2007 though. You shouldn't need the discs to uninstall.