Disc tray will not open

sounds like you have a grounding problem, Try reconnecting them, move the jacks around.

There are two ways toopen the CD drive door if the button just below the drive tray does not work.
Go to My Computer and right click on the drive and click on Eject.
If this does not work then you can manually open the CD drive tray by -
Straighten a paper clip and gently insert it into a tiny hole below the drivetray next to the Eject button. Push the paper clip gently until the drive traypops out, then pull the tray until it is fully out, then you can remove the CDdisc.
If you continue having problem opening with the Eject button, then the CD driveis faulty and needs replacing.

There is a small hole on the front of the drive. Use a paperclip or a safety pin in the hole to push open the disc try enough to pull it open the rest of the way with your hand. Insert the disc, press the button on the drive to close the bay. If the tray doesn't close gently push the tray back in. If no lights blink on the front of the drive, the drive may be unplugged or has gone bad.

Make sure your computer boots from the disc drive by going into the bios and assigning it as the first boot device. Then let it load and do a startup repair.

There should be a small hole in the door.

You can open manually using small metal stick (metal paper clip).
Turn off PC, poke small hole (under the tray) gently. Check the rubber ring (like fan belt that goes to electrical motor), it might too loose.

if you are referring to the cd rom tray there usually is a small opening on the front of disc players that a paperclip or needle could fit through that houses an emergency release button.
try this, it should help

My Gateway model #AR-230 tray would not open after several years of use. Removed the black sheet metal cover from the player to access the tray mounting screws in the black plastic tray frame. By tightening or loosening the little screws on both sides of the front of the tray mechanism, I got the tray to slide out (open) reliably again. The problem is the very close tolerance of the internal tray mechanism with the front case opening causes a mechanical hangup or interference. chemicalladdie

See if you get any error Code If the drive could work enought to open the Tray and close it.
try to play the files on the disc manually.
if the disc you have incerted is detected in My computer(computer in Vista)