I found a huge post with LOT'S of suggestions. It could be related to many things...
First step would be to boot into Safe mode and see if the behavior is still happening. If it isn't you know it isn't Windows related but some kind of system driver (e.g. your antivirus even though you have it disabled).
Other suggestions include thumbnails, file permissions, too many files in a folder, etc... just read through the thread and try some things:
