Mike or others, could you briefly explain the details? It's not very google-able.
How do I measure mem use for Microsoft update? It runs under svchost, not it's own process?
How do I disable?
It's under svchost. On XP, to disable Microsoft Update:
Tools > Windows Update
If you have Microsoft Update enabled, the Microsoft Update site will eventually appear. You may need to install an add-on if you've never been to the site before.
Once the add-on has loaded, you can click on 'change settings' on the left side.
When the page has loaded, at the bottom of the main frame there's an option to disable Microsoft Update in a grey area.
How do I manually get these updates later? Any reccomendation how often?
That depends on what Microsoft products you use, Office being the tricky one as its update system of choice is Microsoft Update. You could temporarily enable Microsoft Update every so often (once a week/month?), pull down the latest Office updates, then disable Microsoft Update (note: this does not disable Windows Update).
Also note that Office 2002/XP is still receiving security patches.
This may be just what the doc ordered for the old Athlon and Celeron boxes.
Assuming that they're running Windows XP, the behaviour that I would expect to see is that on startup, when the update system kicks in, there will be intense disk activity for about two minutes (depending on the spec of the machine and security software), and memory usage for svchost will hit a peak. The peak depends on your configuration, I think Office 2007 causes the largest peak in Microsoft Update memory usage, and I've seen the svchost process hit 300MB on Vista, but on XP I would expect it to hit around 200MB. When it calms down, svchost's memory usage is still much higher than it is on Windows Update, on XP I would expect it to idle at around 100MB. So on Windows XP, in exchange for disable Microsoft Update, I would expect to gain about a minute in startup time performance (as in, the machine starts up completely and disk usage settles down a minute sooner), and on idle about a 100MB gain in free memory. On an ageing 512MB machine this can make a huge different in a user's impression of how quick their machine is.
At this point I would expect someone to pipe in "why don't you upgrade their memory, 512MB is never enough for Windows XP, I recommend at least 2GB (or whatever)". Even with extra physical memory, Microsoft Update takes ages on Windows XP to finish its routine, and if I can trim a system down to say 200MB memory usage (180MB is what I aim for, that's using Avast free as the anti-virus), that leaves the average user with plenty of resources to work with, the machine starts quickly, and another 512MB RAM is unnecessary. Extra memory costs money, and most people prefer not to spend money that they don't need to spend, and if I can't demonstrate an obvious performance difference, it's difficult to make a sale. Some customers need more memory, sure, and it's easy enough to demonstrate then.
On Windows Vista as I've said already, I've seen svchost's memory usage get up to 300MB with MS Update enabled. I think it hits about 100MB peak with just Windows Update, however with Windows Vista it is very difficult to monitor when it has finished its update routine, though next time I have a Vista machine at home to play with, I'll try monitoring its process's disk I/O with Process Explorer.
I've got Office 2007 on my own machine (Windows 7), but I use OpenOffice. I have Microsoft Update enabled here and yet the startup time on my machine is the best I've seen, and the svchost in question uses up about 21MB RAM at the moment, so I can't complain about that