I am not sure if it is really Windows Explorer related, but on my Vista Premium every time I open a folder, the system starts doing "something". I can see a sort of green progress indicator in the address bar and during that time the folder is not responding.

I don't have any indexing service running, and my disks are well defragged. I have more than 50% of the disk capacity free. My process explorer doesn't show where the activity is exactly. I don't have any other programs or services running that need to process something on file folders. The system is virus free as well.
This happens on my file folders that contain files on the local disk, nothing is remote, no network files or shared files or anything like that, just regular local files. This behavior is the same for all kinds of file types.
I have the feeling that it is some kind of configuration related issue, but could not pin point the exact config.
Could not find something useful on Microsoft's site.
Has anyone noticed this and could explain it?