Ive never had this issue before, when i first installed the monitor it would detect it without a problem, and i upgraded to windows 10 still no problem, i decided to downgrade back to windows 8.1 and i did a factory reset after that it couldnt detect the second monitor.
the monitor is a LG flatron w2253TQ
and i have a hp 15" pavilion

im using a hdmi cable to connect my second monitor but no luck.