I believe XP's Service Pack 1a is the proper one to install.
Try this site; http://www.microsoft.com/en-gb/download/details.aspx?id=19751&751be11f-ede8-5a0c-058c-2ee190a24fa6=True
You should not download direct to a USB stick. Instead, download to any computer and then copy over to the USB stick.
Mark
Hi, I have joined to ask if anyone could help me find a place I can download (to a USB) service pack 1 for windows xp home edition.
I have an old laptop that had to be restored to its factory settings and as a result it has reverted back to its original settings (service pack 0.0) It is not connected to the internet, (as I use a 3g Broadband modem / dongle which won't work without a higher service pack).
So - I need somewhere I can download to a USB (not a disk) a full version of Service Pack 1 (not the express one on the microsoft website - as that one requires a web connection).
Thanks for any advice / suggestions.

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