I have managed to download XP SP3 and slipstreamed it with nLite.
IMHO: The source CDs used to build a WinBuilder project, should ALWAYS be 'M$ Original'.
And I do not know what nLite surpresses as 'obsolete' or 'not needed' or what tweaks it adds.
Therefore, in my opinion, you should everytime use 'Bill's original way'
It is different for different OSs, but always same logic:
You can use a batch file like I do:
V:\BCD\cds is the folder on my system where the different sources are stored. You have to adjust to your real world.
REM sp1_de.exe /integrate:V:\BCD\cds\XPP_DE_SP1
REM SP3-ENG.exe /s:V:\BCD\cds\XPP_EN_SP3
REM W2003_SP2_ENG.exe /s:V:\BCD\cds\W2003_SP2_ENG
As you see, different SPs have different cmd lines to slipstream. Currently they use /integrate or /s