Mouse Sluggish For Short While Whenever Document Or Website Loads?

Often when I open a web page in any of my browsers, or a document in e.g. MS Word or Excel, or any file in its associated program, or sometimes even simply a new Explorer window, the mouse becomes sluggish for a few seconds, and in many cases I can hear the hard drive starting up for a second or two as well.I get the impression that the sluggish mouse problem occurs when Windows has to load something or render something new or check something "in the background" while I wait.But wait... it gets weirder: whenever my mouse becomes sluggish like that, the mouse usually overlaps the program that is opening a file, and if I can get my mouse away from that program, the mouse suddenly gets more responsive.This sluggishness also occurs immediately after I've created a new file or folder, or after I've renamed a file or folder.