I have a Dell Inspiron 4000 laptop. Recently a vertical, thin, green line has appeared about 2 inches in from right side of screen. This remains constant throughout all programs. It does NOT appear when I connect to an External Monitor. I know Dell will say 'replace the screen uni't. But I would like to know whether there are any tests or other options open to me - am good with screwdriver and voltmeter...so on.