Bink @ WindowsXP.nu got his hands on the Service Pack 1 beta build 1050 and gave it to IEXBeta.

While the download is only 1.7 megs, I am sure you will have to download another 100 megs before you have it installed. Hit read more for the download link! Download Microsoft Windows XP Service Pack 1 Beta Build 1050 TRY @ YOUR OWN RISK

Big thanks to Xp-erience.org