Thanks for that. I do defrag regularly, not much choice with vista as it defrags everyday, by itself!

rogerg, that will be the disk that defrags. The warning on hibernation concerned the memory (RAM.)

So when I switch off and reboot hasn't that dumped the ram and started clean?

Oh, yes. There are other ways of dumping unused (but reserved) RAM without rebooting. Such as Memcleaner, part of the Iobit Advanced Windows Care app. I downloaded a standalone version, can't remember the link, sorry.
But just hibernating it will not permanently release the RAM.

I've installed Norton AV 2009 and don't seem to have any performance issues at all. In fact Norton seems to take only a few seconds to start. It updates regularly during the day now, not just on fridays ;) and the scans seem to be quick too. It does have something called insight which monitors files which are safe, not sure how effective it is though.

The Windows 2003 Server/XP Resource Kit also has a memory cleaner called ClearMem.