Look at FILEMON on google.com
In the "monitor processes" type of threads, I'd like to have a program that monitors file access originated from background processes.
Often I see my PC (Win XP) hard disk suddenly busy to do a "furious" access to disk.
Sometimes I know why (i.e. Google desktop) but much often I don't, and I suspect some spyware/unwanted process has started.
I use the Windows Task Manager "processes" option to see "at a glance" which processes are getting top priority (sorting by the CPU tag), but is a very tiring and inefficient trick.