Scrolling problem

I had the following problem in 2004 and now I am having it again. I can't remember how I solved the problem.

Here is the problem--After hearing two "beep-beeps" come from my computer, I have had limited control over my vertical scrolling. Sometimes it works fine, but much of the time, the scroll bar begins to slip up or down until it reaches the bottom or top of the page, or sometimes it has a jerky motion. There is also a seizure-like, continous scrolling in drop-down menus on web page forms. The scroll bar also gets stuck at the bottom of the page or, if vertical, the extreme right side of the page. I disconnected the mouse, and the problem seemed to go away, then reconnected the mouse and it worked okay for a while. When the problem returned, I uninstalled and reinstalled the mouse driver, but the problem has returned. Has anyone had this problem? Is it a mouse problem, or something internal to the computer?  I have a standard Dell mouse on a Dimension 2200 that does not use a USB port. Thanks.