They say we should back up our most important files, regularly. Although I've never suffered from any serious system error (thus losing files as a result), it's also very easy to forget which files you should place on your new PC. For example, commercial fonts. There have been many instances where I've spent ages backing up my most important data, moving this across to a new PC and then wiping the old drive, only to find that I forgot to move across a commercial font. This can be of paramount importance if you're responsible for producing company literature using specific fonts.10 Nov 2008