With a PC that does have internet access, go to the Windows Update site and, from the Other Options, select Personalize Windows Update. Tick the box "Display the link to the Windows Update Catalog" and click "Save Settings".
You can now click on the link for the "Windows Update Catalog" which then displays options in the right pane, including "Find updates for Microsoft Windows Operating systems".
You can then search for the updates available for all operating systems and download them for subsequent installation, by burning to CD or whatever.
This was done using Windows 98SE, but it can also be done using XP though it's a little more complicated getting there!
The actual page is:
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