Hi Oldkrany, my professional background is very similar to your own, my areas of expertise were Unix, Windows XP and Cisco routers.
I would like to point out that many banks offer their online customers free Anti Virus/firewall software as does some of the BT broadband options.
Barclays offer Kapersky and BT, McAfee, both excellent products. I have also use the free version of AVG and found it very good.
I agree that any laptop over 3 years old is on it's last legs and not worth upgrading etc. Disposal is best done by a technically competent person, with a large hammer !.
As you say that is the only safe way, destroy the hard disk. Then take the bits to the dump. But make sure the hard drive is smashed, not just the case. Oh, and back up first.
But of course you all back up regularly, don't you ? Think not, how will I cope IF my hard drive fails, rather, how will I cope WHEN my hard drive fails. the hard drive is one of the few mechanical parts in a PC and they do fail more often than many think. BACK UP you data to another drive, or better still the cloud, often.