Sp3 brings in a lot of stuff that Vista has.

From:
http://www.winsupe...com/faq/xp_sp3.asp

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.

I read something about the built-in firewall too...but the overview doesn't really make mention of it.

i havent run into this at work or at home. but it seems that there is a possible issue with SP3 and "big OEM" built machines using SP3 and an AMD cpu. im too much of a control freak to own one of those desktops, laptop is an intel-based dell.

full descriptor and link in the link below.

http://msinfluenti...alling-xp-sp3.aspx

edit 1130h: another interesting bit from the news today.

http://www.informa...rticleID=207600950

"Some users may balk at a feature in XP SP3 that prevents them from downgrading their browser from Internet Explorer 7 to the older IE 6 once the service pack has been installed. XP SP3 also won't install on systems running beta versions of the yet-to-be released IE 8."

so in short, if you have upgraded to IE7, then apply sp3, you cannot uninstall and go back to IE6.