I just discovered that Windows XP wants to install several updates. What is the description for three of the four?

A security issue has been identified that could allow an attacker to compromise your Windows-based system and gain control over it. You can help protect your computer by installing this update from Microsoft. After you install this item, you may have to restart your computer.

Really helpful, huh? Makes it easy to know what is being changed. Nice to know that my machine may be vulnerable to an outside attack, but I don’t know what software or part of the OS renders me defenseless.