As I understand the bulletin, Microsoft will not be releasing MS09-048
patches for XP because, by default, it runs no listening services or
the windows firewall can protect it.
Quoting http://www.microsoft.com/technet/security/bulletin/MS09-048.mspx
"If Windows XP is listed as an affected product, why is Microsoft not
issuing an update for it?
By default, Windows XP Service Pack 2, Windows XP Service Pack 3, and
Windows XP Professional x64 Edition Service Pack 2 do not have a
listening service configured in the client firewall and are therefore
not affected by this vulnerability. Windows XP Service Pack 2 and
later operating systems include a stateful host firewall that provides
protection for computers against incoming traffic from the Internet or
from neighboring network devices on a private network. ... Customers
running Windows XP are at reduced risk, and Microsoft recommends they
use the firewall included with the operating system, or a network
firewall, to block access to the affected ports and limit the attack
surface from untrusted networks."
-eg