The first test when this sort of thing happens is to try another mouse. For example, if this is a USB mouse, try a PS/2 mouse. Or if this is a wireless mouse, change the batteries and also check that the wireless receiver is no obstructed.
For the last week my Windows 7 computer selects stuff all by itself whether on the desktop, in the browser or in applications like Paintshop pro. Bookmarks are picked as I pass over them, I can't use certain tools because they select at anytime and programs open as I pass over them!!! "Activate a window by hovering over it with a mouse" is unchecked. I also unchecked a similar item in the start up menu customization menu. I also find and used something to restore the Window default hover in the registry . My problem persists, help!!