Question for Computer security experts

[DanG]

AVG antivirus is free, it works well and they update it frequently enough that it's effective.
Microsoft Antispyware. Currently in beta form, it's a great program to have (partially because they bought it from someone else called Giant).
Spybot Search & Destroy. Another freebie, it had a great feature called immunize. Install it, update it and then by running immunize it blocks ~8000 different things from getting in.
Google Toolbar. Another free one, blocks most of the popups you will run into on the internet.

If it's for a younger kid and you're using windows xp, I STRONGLY recommend making a guest account for the computer. The guest account has limited privelages and they can't install or make any system wide setting changes.

A lot of people lately are pushing Firefox as a much better browser than Internet explorer, but in my opinion, for a kid using a guest account with the spybot search and destroy immunizer in use, Internet explorer will be just fine.