One of our Windows 2003 started logging errors in Event Log with a search service trying to index the contents of D:\Program Files\Trend Micro\ and failing.
I'd previously told "Indexing Service" to exclude those folders (via its snap-in to the Computer Management utility), and the service now even disabled.
It appears to be that the problem was now with a different service, called "Windows Search", which apparently supersedes the old Indexing Service. All the doco mentions using GPO to configure it (!) but it turns out there's a control panel applet, and the Trend sub-folder PCCSRV was listed there specifically for indexing. I wonder if this happened because it is shared over the network? Anyhow, removed that and it now seems to be running without errors.
Bloody computers - no sooner do you get the hang of how something works, and some bright spark goes and supersedes it!