After all my updates on Chris' Microsoft laptop, it still spends between 10 and 15 minutes of saturated disk activity after each boot or resume. Spent some more time looking at (and learning) the task manager, and found the problem: a process called SanService.exe was performing up to 10 MB/s of consistent disk access during the whole time. And how about that, Google found it for me: it's part of Sophos Anti-Virus. That's something I know nothing about. Is it necessary to scan at startup time? I'll have to do some more learning.
ACM only downloads articles once. It's possible that this article has changed since being downloaded, but the only way you can find out is by looking at the original article.