I've been using this, along with Spybot S&D to go with my Norton anti-virus. No problems with spyware or viruses in the last couple of months.

XP sp2 with everything updated always

Or you could browse with Firefox and not need any of those?....I've been doing that for over a year with great success.

Same here speedy. But some of the nasties are trying their worst to sneak in under the radarscope by hook or by crook. Defender runs in the system tray, on guard 24/7 as long as the computer is running.. Same goes for Ad-Aware professional. Right now, MS's defender is beta, meaning that are bugs in it. If you really are worried about the bad boys getting in, install Firefox and buy Ad-Aware to run full time.

^^^True, true. I find that the Ad Aware that runs full time doesn't eat resources like Norton would. Firefox + Ad Aware = Smooth running comp.