Microsoft may have inadvertantly let the cat out of the bag when it posted the
Microsoft Support Lifecycle
In general, that posting really means nothing, because the service pack has not officially been released, in fact, its just simply stating that the RTM date is 3-31-2008. Microsoft is holding off on delivering the update to customers until at least mid-April, according to company officials and sources close to the company.
Windows XP Service Pack 3 will contain hotfixes and updates released since Windows XP SP2. It will also include an expanded set of product keys for Windows XP Professional that were originally introduced in Windows XP SP2c.
However, there are a few new features included in Windows XP SP3 and those are as follows:
Network Access Protection compatibility. Announced years ago, this feature allows Windows XP machines to interact with the NAP feature in Windows Server 2008. This functionality is built into the RTM version of Windows Vista as well.
Product Key-less install option. As with Windows Vista, new XP with SP3 installs can proceed without entering a product key during Setup.
Kernel Mode Cryptographics Module. A new kernel module that "encapsulates several different cryptographic algorithms," according to Microsoft.
"Black hole" router detection algorithm. XP gains the ability to ignore network routers that incorrectly drop certain kinds of network packets. This, too, is a feature of Windows Vista.
And that's about it. Nothing dramatic, as promised.
Microsoft has said that there will not be any integrated SP3 release for Windows XP Media Center Edition or Windows XP Tablet Edition. That means you won't be able to buy or obtain a complete Windows XP Media Center Edition / Tablet Edition SP3 CD. In addition, users of Windows XP Media Center Edition or Windows XP Tablet Edition will only be able to update to Service Pack 3 through Windows Update.
All languages will now be released in two waves. Earlier, Microsoft said that languages support for Windows XP Service Pack 3 will be released in three waves. What was previously identified as wave 2 and 3 have now been combined into a single wave 2.
Overall, despite what the others have said about the XP SP3 release date, don't expect to see it for about another 2 weeks (somewhere on or around April 15-18). In addition, for those of you out there using any other language than Chinese (Simplified), English, French, German, Japanese, Korean, and Spanish you will be waiting an additional 21 days after the general availability of Windows XP SP3 to get your hands on it.