jittery mouse cursor

[paulclmnt1]

I just installed a copy of windows 7 ultimate 32 bit onto a Dell Latitude XT that had Win Vista. During the driver installation session I noticed that the mouse has suddenly acquired a bug, when it restarts and is at rest the cursor is jittering and won't respond to the mouse commands until I enter my password. When I move the mouse it then stops jittering. Also when a dialog box opens for a requested response to an app. or utility to be opened it jitters and I have to use the arrows to select yes or no. Any ideas?