Download details: Windows XP Security Patch: Buffer Overrun In RPC Interface Could Allow Code Execution

Download details: Windows XP Security Patch: Buffer Overrun In RPC Interface Could Allow Code Execution: "A security issue has been identified that could allow an attacker to remotely compromise a computer running Microsoft® Windows® and gain complete 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."

I personally had a demonstration of this.