I had some time today to work on one of the teacher's computers so I had control over anything running. First, I looked up a guide to help refresh my memory about the Task Manager (too many years since my course) and I found that this article was helpful for me: http://www.techexams.net/technotes/xp/performance.shtml
I was able to recreate a slowdown while working on the computer and as I was doing so I watched the Task Manager to see what was happening. My opinion--shared by my boss who often gets in early to answer e-mail from parents--is that the most trouble occurs at initial boot for the day when not only the Operating System is loading and Windows Update check might be running but also due to our Trend Micro Client/Server loading, updating, and starting its continual background scan. I notice that on my own computer at boot but I don't notice it as much on any computers that are not on the Domain (and therefore have something other than Trend Micro running).
What I did today and what I suggest for anyone who wants to troubleshoot performance:
1. I checked the amount of free space on the hard drive since Windows needs at least 15% free to be happy and won't even run the disk defragmenter without that space available.
2. I went to Add/Remove Programs to see what was there and removed anything not needed any more that might simply be running as a background task unknown to the user. Just one example: I found an old Epson printer application that is meant to monitor ink levels. Despite the printer having been removed the ink monitoring software remained and showed up as a running process in the Task Manager.
3. I checked the System Properties to see how much RAM Windows was using and how much it was sharing with the onboard video. Much to my surprise, all of the 512 MB was listed for the Operating System with nothing allocated to the onboard video. For other computers that I've worked on I usually see at least 8-32 MB RAM allocated for video.
4. I changed the Virtual Memory to the suggested levels in the article referenced above: 1.5 x RAM minimum and 3 x RAM maximum. It had been set much lower.
5. I turned off indexing.
6. I looked at the "setting priority" step in the article and considered changing one of the processes to see what would happen but Windows gave me a very stern warning about changing anything so I didn't do it. I know that the warning might safely be ignored so I will consider it for another time.
7. I updated CCleaner and used it to clean up clutter, check the registry and manage any other background tasks that I hadn't managed otherwise.
That's as far as I got. I didn't change the Visual Effects but have done so for other computers.
All the time that I was doing this and doing other tasks such as updating Firefox, Flash, and Java I ran the Task Manager. At times the CPU ran at 100% such as when Windows was modifying my indexing request or when launching the browser or Word. More often, however, I saw the CPU at a modest usage and the RAM running anywhere from about 260 MB (for no applications running) to 715MB for streaming audio online with only one tab active in the browser.
Based on the RAM usage and the teacher's needs to be able to stream media if pertinent I ran a scan from Crucial.com to find the correct memory (it uses the older DDR) and we will double what the teacher has to 1 GB. Meanwhile he will give us feedback as to whether anything I did today helped or not. All teachers will be advised by my boss not to expect to boot and start work immediately in the morning due to Trend Micro running. Usually five minutes will be enough for it to finish its update task and then it will release the CPU.
I understand what you mean about hitting the cable modem all at once but that hasn't been too much of an issue this year compared to last year when we had a router firmware problem slowing everything down.
I'll also keep in mind what you said about MS Office applications and will try to check that out the next time I have an opportunity.