I have had a 'free' virus checker on my laptop for a while now. Every night at 8pm it starts and takes a good couple of hours to scan the files. It really slows everything down and 9 times out of 10 I end up stopping it so that I can use my machine.

My machine has been slowing down a lot, so last night I got right fed up with it and bought a proper virus checker. The machine is only marginally quicker, if at all.

However, when I fired it up this morning and started downloading my emails it found a Trojan hidden away in them, so it has already paid for itself.