The cursor on my Compaq laptop becomes unstable after only 10 minutes of use. Typically it jumps vertically when the left button is pushed. It happens with an external monitor or with the laptop display. Although the PS2 external mouse shows up as OK on the Add/Remove hardware screen, it does not respond to a PS2 or serial mouse. Sometimes it is possible to get one effective click by setting the cursor under the icon, but a double click jumps above the icon and does not activate its program. Does anyone see any help for this?