around the bottom magnet there is a black layer, kind of a gripper. which may full of dust causing it not to grip the disk. try giving it a clean with a cotton bud and cleaning alcohol.
i got a ps2 off ebay for £1.05 and that was the problem
what is the model of your ps2
sound like the dvd side of the laser has gone ..test it with a cd-rom game first blue underside....if spins up then the laser is only good for cd-rom games ..and wont play dvd-rom if no spin after testing... sometimes the la chip or ba chip depending of the model of ps2 has blown ,that will stop it from spinning or even a completely dead laser will stop it too......: multi :