There are 8 screws on the bottom of a ps2. 4 are hidden under the rubber feet which you can easily get off with your finger or a screwdriver.
I too had a problem with my PS2 not playing anything, mine repeatedly clicked whenever a dvd/cd was inserted. If this is what you are getting your lens may need adjusting. Its easy to do - This guide sorted mine out http://arstechnica.com/articles/paedia/hardware/ps2.ars
chris
December 2004