I'd stay away from McAfee and Norton both, seems like they've been on a slow decline these last several versions. McAfee in particular has some really stupid, not so user friendly quirks about it.

There are free alternatives as others have suggested, although I've learned to not have much confidence in them. The timeliness of definition updates with free products can leave a lot to be desired, and often times features you really need are left out, or dangled in front of you only to be enabled if you pay them.

But even something ho-hum is better than nothing at all, especially if you leave your PC on all the time connected to the web via broadband.

If I had to recommend one product to someone looking to keep their rig problem free at this time, it would be Kaspersky 7.0

Very impressed with it.