Yes, my Toshiba is aging, over two years old now. Its 512MB memory and 1.4 GHz processor are challenged in comparison with newer systems. Every saving of resources matters, therefore, but at the same time you have to have protection.
Recently I opted out of Avast! antivirus and tried AVG8. Bad choice, at least in terms of resource use. I do have this thing called Anvir Task Manager Free which keeps me well informed about what is going on under the bonnet; yes it also uses resources, but not much. Well, now I have ditched AVG in favour of PC Tools Free Antivirus, and my computer is much happier. (I already had the PC Tools Firewall, so I figured the two programs should be happy together.)
PC Tools AV and Anvir open simultaneously; the AV is updating, so the CPU usage at this point – see extreme bottom left just above the bottom bar – is 100%, but memory usage is only 72%. That would have been 100% before I switched. Note the thorough event log.
About Avast! – it is good, but it is also a bugger to uninstall. You have to download a tool to do it, and it can only be done in safe mode. Very fiddly. At least AVG uninstalls easily. And yes, I have several good tools for cleaning up after uninstalling – so necessary as almost always there is mess left behind – but that can keep for another post when I am feeling geeky enough…