XP analogue for softwareupdate command line utility

Have a look at MBSA (Microsoft Baseline Security Analyser) and the tools from Shavlik. If you've got reasonable network connectivity between the PCs, try using remote desktop to perform the updates.

http://www.microsoft.com/technet/interopmigration/unix/sfu/default.mspx
http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/ts_cmd_mstsc.mspx?mfr=true

Thanks for the response.

My interest lies in increasing productivity by finding alternative methods (specifically using CLI) to keeping my clients updated without having to tax the processor, or even have the user log out (except on necessary reboot).

I've found articles on how to launch remote desktop from the command prompt (though I'm not sure why you'd want to), but what I want is to connect to the command prompt of a remote XP box.

What I'd like is to have a command prompt at a CLI for a remote Windows machine that a domain user may or may not be logged into, and be able to check logs, download/apply update packages, whatever, administrate the machine.
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Is mstsc the backend of Remote Desktop (i.e. sans GUI)?

Are these client machines part of a single domain, or individual boxes scattered across multiple networks? If the former, just set up a box to serve SUS, and modify the AD group policy for the update interval of your liking.

And that's on the command line, is it?