Playstation 2 plays some games and not others

[Philor]

I bought a secondhand Playstation 2 for my 5 year old daughter. I bought a couple of games and they work fine. I have just bought another 2 games and they do not work, I tried them on my sisters playstation and they work fine.

Has anyone any ideas what could be wrong with the playstation.

[Mattk]

what colour are the discs ?

silver = cd

purple/blue = dvd

maybe its only cds or dvd's it doesnt play either way it sounds like the drive is knackered !

[Philor]

The ones that work are both silver.

The ones that dont are purple and black.

Does this make any difference?

[WoWo]

When I took my PS2 in to trade it they tested both Blank and silver discs, they said that some older ones had trouble playing one or other of the discs, not sure why.