What is in Windows XP Service Pack 3? Just take a look at Microsoft KB Article 946480, "List of fixes that are included in Windows XP Service Pack 3", published today. That is a some list.
Have you ever wondered why people who analyze HijackThis logs and propose fixes for malware removal at some time during the process also instruct the person receiving help to install the latest service pack? The reason is that, in addition to other patches and fixes, Service Packs include all of the security updates issued since either the time the software was released or last the Service Pack.
Our goal is not only to help get the infected computer clean but also provide suggestions to help the computer owner keep it that way. Having Service Packs installed is one step in that process.
List of Fixes in Windows XP Service Packs:
Windows XP Service Pack 3: Microsoft KB Article 946480
Windows XP Service Pack 2: Microsoft KB Article 811113
Windows XP Service Pack 1a: Microsoft KB Article 324720