Since upgrading to XP SP2 a long time ago, I constantly get nagged by a popup message that tells me my computer might be at risk because I don't have antivirus software installed. Here's how to turn off that annoying message at Taskbar. 
To Disable this popup -
1. You will want to open up your control panel, and then open the Security Center icon.
2. On the left hand side of the security center window, you will see a resources section.
To Disable this popup -
1. You will want to open up your control panel, and then open the Security Center icon.
2. On the left hand side of the security center window, you will see a resources section.
3. Click the bottom link, "Change the way Security Center alerts me"
4. You can choose which alert to disable here. unchecked all the botton checkboxs.
Now Windows do not show any more annoying popup at Taskbar!
