I was just looking at Samsung's site regarding this issue. It is most likely a line of dead pixels. Direct from their site: "The thin red, green, blue, white, black, or yellow line you see running through your LCD monitor is most likely a line of dead pixels. To fix this problem, you will have to get your monitor serviced or, if the monitor is new, replaced. To set up a service appointment, contact Samsung Customer Care at 1-800-Samsung (1-800-726-7864). Have your monitor's model number and serial number on hand when you call." http://erms.samsungusa.com/customer/sea/jsp/faqs/faqs_view.jsp?PG_ID=1&AT_ID=15336&PROD_SUB_ID=28&PROD_ID=-1
Please try to connect the monitor to another PC, if problem still exist then probably there's an internal problem in the circuit board of your monitor wherein an elecronic part/s might be cold soldered / defective. I recommend to bring the monitor to an authorized HP service center to fix the problem. If the monitor display is good if connected to other PC, then your previous PC should be checked if the VGA card (if there is any) is properly placed to its slot & working properly as well as it cables & connections. regards
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