Thank you for your replies. I use both, paid for versions of antivirus and a spy where programs. I am a bit paranoid therefore I don't think it's a good idea to reveal which versions are used because it makes me think that maybe that would give hackers and advantage, knowing what they were up against!
I recently went to the "shields up" web page which tests your PC for security. My PC got a clean bill of health, but interestingly another PC I use, (one for the kids) which just has a basic unregistered version of winXPpro (No Downloaded upgrades) on it also got a clean bill of health! this has access to the Internet frequently, and the kids download anything and everything they fancy!
So I wondered is the "shields up" site any good at detecting problems with your PC? Or are there any other sites which offer a similar service which you could recommend.