You have probably heard about this already, but I just thought I would let everyone who hasn't know.
Get it hereFrom Microsoft
Windows XP Security Patch:
Unchecked Buffer in UPnP can lead to system compromise
This update resolves the “Unchecked Buffer in Universal Plug and Play Can Lead to System Compromise” security vulnerability in Windows XP. Download now to prevent a malicious user from compromising your computer, or using it to interfere with another computer's operation. The vulnerability results because the Windows XP Universal Plug and Play feature does not correctly validate inputs before using them. The patch also eliminates the vulnerability discussed in Microsoft Security Bulletin MS01-054.