Last month a vulnerability was disclosed that affects all versions of Windows. If exploited, the attacker would gain what is being called "Big Brother power" over a victim’s computer.
Microsoft, not wanting to share the Big Brother power that they already enjoy over their victim's computers, quickly and jealously issued a patch for the flaw. Presumably the update will also fix XP-based computers, provided they've had the POS hack applied. Non-POSers should make use of one of the work-arounds mentioned in the link below. But don't just take my word for it. You can take it from security expert Wilford Brimley:
"NetBIOS fix - it's the right thing to do, and a good way to do it. Goo goo g'joob."