You have to have that service checked for internet time; for Services (at Start/Run) type in:

services.msc 

Windows Time

Maintains date and time synchronization on all clients and servers in the network.
Every now and again when you connect to the internet Windows will synchronize your clock to the exact time on its servers. While some may like that idea it is really not necessary and is best set to Disabled. Right-click on the time in the corner of your screen, select Adjust Date and Time, click the Internet Time tab, and check the box.

Thanks, but which service is it that needs to be enabled? "Windows Time" says that it is started and start-up type is automatic.

Thanks, but as per my original post, my complaint is that I do want Internet Time enabled but the tab does not even appear in the preloaded version of XP Pro on my Dell, obviously due to some quirk about the Dell version of XP Pro.

What I want to know is how to make the Internet Tab available?

Red Jellyfish,

Is your computer on a domain? See this. The Time Tab is not missing from Dell OEM copies of XP Pro by default.

Ah - all is revealed - many thanks.