Ok so i have a ps2 slim. ya know, the silver one? well whenever i insert a disc it will not spin. it turns on & works great but it just wont spin discs.the little disc stopper (small & grippy thing to appropriately slow down the disc causing it to stop) is stuck to where the disc is unspinnable however i can freely move it allowing the disc to spin when i spin it but only if pressure is applied. once i let go it goes back to to how it was. plz help im not really sure if i can fix it somehow but i would like to know if there is a way how. if not oh well....

SOURCE: My PS2 Slim plays music, black and blue discs, but doesn't play silver discs nor DVDs.

Is this a new problem or has your PS2 always had this issue? You cannot adjust the laser at all and are likely to damage it if you try, you can however clean the laser lens with a CD/DVD cleaning disk and you'd be surprised how often this resolves disk read issues. Some of these units did have a production fault that prevented them from reading DVD's, if your PS2 has had this fault since new and/or is under 12 months old you could probably have had it repaired/replaced by Sony but by opening it you will have invalidated you're warranty.

SOURCE: Disc won't spin. Disc doesn't show up in browser

You got a problem with the lasers data getting back to the Motherboard.
One of these could be your problem

1. Laser lens is melted. Look at the lens with a magnifying glass to see if it or its supporting frame is melted. REplace the laser in this case.
2. The ribbon Cable going from the Laser to the motherboard is damaged or loose.
3. Your laser is burned out. Press the two interlock to override the door being open, to see if the laser even lights up. 2 switches, one at rear left corner, one behind the On/reset switch.
4. Your Laser is dirty and needs cleaning look at it with a magnifying Glass to make sure you got it clean. Use Q-tip and window glass cleaner, not alcohol.

SOURCE: silver discs

i got the smae problem

SOURCE: my ps 2 slim will play blue discs but not silver discs?

sidekicklova is a ***

SOURCE: PS2 Slim New Lens, Not Spinning

Hi guys,
Well, there is 2 switch. one at  the back left of the cd tray and one one the reset /power switch. both sitch have to be close in order for the disk to spin. 
If you try this dont forget to put a disk on the spindle as you will start the laser. this is for your safety. then, if the disk does not spin, then you can try replacing the laser. or at least verify the ribbon cable that is hook to it. if the ribbon cable is not well inside the plug the laser might move but again the disk won t spin.
it is related to each other, the PS2 seem to verify the laser prior to start the spindle so what ever happend to the laser affect the spindle.
and then, if you buy a new laser lens, don't forget to remove the soldering bridge. it is a small ball that is use to avoid static while shiping the lens. 
most of the seller will include a small peace of paper with procedure and also there is web site with picture of this soldering bridge.
I replace some of them, and I have to say that the small plastic lock for the ribbon  cable to the lens has been an issue and the soldering bridge another one.
but I got most of the PS2 back and running by replacing the laser.
I hope this will help you.