While my computer was off, I connected an s-video cable to a TV to create a dual-monitor setup. The boot-up seemed to give the s-video port priority, as when i turned on my computer it was the TV displaying my start-up screen instead of my usual monitor, but after the windows logo was displayed the TV abruptly lost the connection. meanwhile my computer monitor indicator light was green, indicating it was receiving a signal, but the screen was black. When i attempted to reboot after removing the s-video cable, my computer monitor would still give me the "reiieving signal" light, but would remain black. I turned my computer off again and connected the computer monitor's VGA cable to my TV, which then worked perfectly. So it strikes me that something I did made my computer ignore my monitor. How can I fix this?