You should consider installing Service Pack 2 as soon as possible
On August 9, 2004, Microsoft released SP2 for Windows XP. SP2 is the latest collection of updates for Windows XP.
See the Windows 2000/XP SP Slipstreaming page for info on how to integrate SP2 into your existing media.
Windows XP Home or Professional with Service Pack 1 or Service Pack 1a requires the following security-related patches (If you don't know about SP1a or if you want to read about it go to my Windows XP SP1a Info page):
MS03-017 : Flaw in Windows Media Player Skins Downloading could allow Code Execution (817787) (Only if you still have the original WMP for XP)
For the full list of Windows XP post-SP1/1a fixes please visit the following URL:
Note that this list contains ALL fixes, not just the security updates. Depending on your configuration you might not need to apply all the fixes listed above.