Gripe of the day; explorer's desire to scan entire folder trees

OK, so who was the bright spark that decided that when I click on a folder at the root level of a drive Explorer goes off and scans the entire folder tree from that point down before expanding the one folder I’m interested in? More importantly, can I turn it off? Surely the most you really need to do when I click on I:\Blah is list the files and directories in Blah and do a lazy directory content check in the background to see if you need to put a + next to any of the directories in Blah… At present, on XP SP1 it seems that the directory check isn’t a background thing, so I have to wait for it to complete, and when the sub dirs contain many many files this can take too long…