(2-part post):
Removing Norton completely isn't 'a bit of a nightmare'. You simply download the removal tool and run the software. (All the other stuff on the Symantec website is about saving your product key. If you're going to do a fresh install of Norton 2008 or, better, use something completely different, you can ignore it).
If you were to install Norton 2008, from PC World, it would probably be best to uninstall the 2007 version first. However, as has been repeatedly stated by a large number of the 'regulars', here on AB's Technology section, installing any version of Norton is complete madness anyway. Both Norton and its biggest 'paid for' rival, McAfee, are known to be 'resource hungry' and slow many PCs to a crawl. The computer press repeatedly advise against installing them.
You should never need to pay for security software. The free stuff repeatedly scores as well or (usually) higher than commercial programs in independent tests.