Rather than chewing up your bandwidth with a whole OS + service pack download it would be much better to create your own XP SP3 cd.
Aside from being much faster and easier, it is also more secure. When you download operating systems of this nature it is unknown if there has been any tampering and / or malware has been inserted.
You will need to download nLite (freeware):
http://www.nliteos.com/
and SP3 for XP 32bit (from Microsoft severs):
http://download.windowsupdate.com/msdownload/update/software/svpk/2008/04/windowsxp-kb936929-sp3-x86-enu_c81472f7eeea2eca421e116cd4c03e2300ebfde4.exe
Because SP3 includes all hotfixes and patches contained within SP1 & 2 it is the only service pack you will need.
As a side note, you can also include the SATA drivers into your new cd with nLite, this means you won't have to hit the F6 key when prompted.
You can also include your product key in the installation so that you won't be prompted for it. (Create an unattended install)
You will need to first install nLite. Once installed run it with you genuine XP OS cd in the drive.
Once nLite has copied the Windows installation files to your pc the next screen will have a list of choices. The very first choice is service pack so you will need this. I've listed below the options I use. You may find the others useful though.
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Service Pack (to incorporate the SP3 you downloaded into your cd)
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Drivers (for Chipset, SATA, RAID etc or even printer drivers if you want)
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Unattended (So you can input the CD key without having to during installation)
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Bootable ISO (You will need a burning utility to burn it though, I use
http://www.ntfs.com/iso-burning.htm (freeware). Very easy, all you do is right click ISO and select "Burn ISO".
Once you have the ISO burned you should have your own custom made SP3 cd.